Section Four, Session

TechnicalSession F{o. 6 Srfety Developmentsof Goods Vechiclesand Buses L. Strandberg,Chairman, Sweden

ImprovedCommercial Vehicle Conspicuity and SignallingSystems

therefore,that countermeasuresaimed at RussellL. Smith' It would scem, a smallpcrcentage of vchiclescould leadto a signil'icant J. Burger, William redrrctionin a rclativelylarge percetrtage oi'i'atalities, Kenneth Ziedmnn.and Onc crbviouscountermeasure would be the improved Msrk Mulholland visibilityor conspicuityof largetrucks. 'l Vector Enterprises,Inc. his papersummetrizes a 3-[year project,fundcd by the U.S. f)epartmcntof Transportationand dcsigned to developand cverluateinrproved conspicuity systems for Abstract largctrucks.

Vehicle-into-large-truckaccidents produce a dispro- Rationale portionatelylarge number of fatalitics.It ishypothesized a truck's visibility or conspicuitywill Imposing new Federal lighting and reflector system that increasing 'l reducethe numberof vehiclcscolliding with trucks. he requirementswould clearlyirnpact directly on thetrucking purposeof this projectwas to analyzethoroughly this industryand indirectlyon everycJriver. l'hus, prior to the specificaccident problem, estabtish inf ormation require- developmentand test of proposednew consptcuity ments of other drivers,revicw the stateof the art of systcms,every el'fort was made to provide a thorough conspicuitytechniques, dcsign and conducta seriesof statementof the Problettt. conspicuityexperirnents, design a newintegrated lighting The proicct was composedof the following tasksand system,dcsign an augmented,lou-ctlst suhtasks: and rrrarking 'l'ask retlectorizedsystem for retrolitting on largetrucks, and l. l: Define and analyzethe vehiclc-into- fielcl test the augmented system on lleets of trucks. truck collisionProblem. Approximately 2,000 trucks were fitted with the aug- r Iteview rclcvantliterature mented $ystetn,and accidentrates are curlcntly being . lnterviewtrucking comPanies monitored and compared with those of a matchcd . . Analyzeaccident data controlgroup of 2,000tlucks. At thetime of thiswriting, r Developfunctional requirementsof drivers the 2-yearficld stutly is nearingcomplction. About 70 r Analyze retrorellectiveand fluorescent , percentofthe total accidentscxpected have been analyzed' materials and thc resultsthus far indicatethat the trr.rckstreated r Evaluatc current Federal Motor Vehicle with the reflectorizedsystems are being hit at a lower ratc Safcty Standards (retrofit) than arecontrol trucks. lncreasing conspicuity, therefore, 2. Task 2; Designand evaluateaugmented appearsto be an el'lectivemethod of reducingvehicle- and newintegrated lighting and rcflector systetns. into-truck accidents. r I)csign various conspicuitysystems and conduct laboratory,l'ield experiments t Designa specificlow-cost augrnented system Introduction for field tcstingon truck fleets I Preparea detailedplan for conductingthe ': fiehl test of thc augn'rentedsystcrn Purpose r Designa new,integratcd conspicuity systcm for original equipmentmanufacturc '[ask (.onduct Large trucks' equal to or in excess of 26.000 lb 3. 3: field test of the augmented constituteless than 2 pcrcentof the total populationof systcllton selectcdtrr.rck lleets. vehiclcsin the [Jnite

841 Experimental Safety Vehicles

The following sections emphasizemajor findings, Scenarioanalysis de monstrated that a truck conspicuity analyses,and considcrationswith respectto the above systerncommunic-atcd general rathcr than specif ic inlbr- three tasks.Vastly more detailcdaccounts can be found mation with respcctto its dynanrics.For cxample,the in (3) and (12),As of thiswriting, the projccr is not quite currentsystcm for indicatingchanges in velocityhas only complctcd,there being a few monthsremaining in Task 3 two lttates:the brake light is eitheron or off. Thc vehicle 'lask licld tcsting.The resultsreported I'or 3 reprcsent caneither be stopped, accelerating, maintainirrg a constant approximately 70 percent of the total accider-rtdata specd,or decelerating,and, with regardto accclcration expectedin the field test. anddeceleration, the rateol'change can valy substantially. Thus, the current systsmrelies on the drivcr to perceive Task l: Defineand Analyzethe Vehicle- cherngesin rateof closurc,an extremclydifficult pcrceptual task,particularly at nightwhere much of thevisual input Into-Truck CollisionProblem is sevcrely redrrced. The analysesof vehiclc-into-truckaccidents and associatedsccnarios clearly ind icated a needfor improved Analyze Accident Data truck conspicuitysystcms that would providedrivers with the following specificinlolrnation on the l.ruck's Reviewsof extensiveanalyses of a numbcr of accidcnt positionand dynamics: r data bases reveal that large trucks are struck about Prescnceof a vchicle equally often in thc rear and side, the latter including r lndicationol'a truck r both sideswipcsand perpcndicularimpacts. They are also f)istancc equallyolien struckat nightor in dimly lir cnvironmcnts ' Speed as during the day and are struckahout equally often on r Whctherit is maintaininga constantspeed t rural and urban roadsthat are both lcveland graded. , Whethcris it accclcrating r Rear impactstcnd to occurwhen thc truck is travcling Whether it is decelerating r straightahead and rnovingslowly or stoppingor stoppcd Whetherit is stopping r on the roadway.The followingr-lriver eithcr ( l) d ocsnot Whetherit i'r stopped r seethe truck at all, (2) seesthc truck but lnisjudgesits Whetherit is backingup r motion and/or distance,Qr (3) corrcctlyperceivcs the Whetherit is rnaintaininga constantdirection r truck's dynarnicsand distancebut not within sufficient Whcthcrit is turning time to avoida collision. A numhcr of techniqucsexist for satisfuingthe above Trucks are struck perpendicrrlarlyin the side most functional rcquirements,Unfortunately, most of thcm would bc too costly to be corrsidcredseriously at this oftcn when turning or beingirstride lanes, e.g.. backing. 'fhus, making U-turns, etc., but are ollen sideswipedwhen timc. lessthan optimal soh.rtionsrnust be sought travcling straightirhead. that are, r'rcvcrtheless,signilicant irnprovcrnentsovcr In view ol'thc foregoing,therefore. it would appcarthe current systems.Such solutionsmust derivefrom an conspicuityproblcm with largctrucks is not restrictedto undclstanding of how drivers detect and identify the nighttimeconditions or specil'iclighting and marking presenccof a truck and acquireknowledge of itsdynamics. It hasoften been said that mostaccidents are wholly or systerns.l rucksare apparerrtly inadequatcly conspicuous 'l duringthe day, and boththeir sidcs and rcar.cnds seem in principallycaused by inattentivcrbchavior. hus,cletcction needol' incrcasedconsnicr.ritv. perlormanLrcdepencars.F,ach sccnario was analyzed environment.llurg and Ilulbert(2)and Burg and Becrs( l) at a level of detail necessaryto identil'ythe functional demonstratedthat the uniqucshape of a stimulusis of recluirementsof truck communicirtionsystcnrs, These considcrableimportance in attracting attention and scenaritr$included vehicle lorlations. directions of move- establishingrecognition. For examplc, reflector.scom- ment, and varying speeds.Stopping distanceswere pletely or.rtliningwhccls attract far more attentionthan computedthat indicatcdthe distances at whichthe driver do nondistinct ref'lcctorsarbitrarily locateclon bicyclcs ol'thc strikingvehicle would havcto applythe brakesto and motorcycles. stop ol slow sufficientlyto avoid a collision.Dyrramics of Drivers employ subjectivejudgments in determining both vehiclesand systemreirction times werc included in distances and dynamics of other vehicles.Carefully thc computirtions. controlled lahoratory experiments indicate that size

842 Section4. Techniaal^Sessloas changesof an object moving in depth constitute the to observationangles. At an observationangle of 1.0o, dominantcue in iudging motion in depth(9,10).Appar- relativeintensity rnay typically be only onc-tenththat of ently. thc largerthe objectappears to an observcr,the 0.l'. smallerthc changein sizcnccrssary to detectmotion( I I ), The retroreflectivcclevices relevant to trucks include The speed differencesin vehicle lollowing become materialscontaining ( I ) sphericalglass bead elements, or increasinglyimportant the closerthe followingvehicle (2) cubccorner or prismaticelerncnts. In eachcasc, it is approachesthe leading vehicle. lttleson ( 195l) notedthat theclements that rellectthc incidentlight.'l hc glass bead whilesizc changes in an objectprovide motion cues.thc materialsinclude thosr havingbeads paltially imbedded judgment of distanccol an objectdepends on a priori within a supportingsurlace such as paint and paftially 'l known characteristicsol the object. hus, if an object exposedto the atmosphereand thoschaving beads that projectscharacteristics that provideno cuesor ambiguous are completelyirnbcdded within a transparentmatcrial. cues, ne basis exists {'or cstirnating its distance. An Thc exposcdbead designs generate greatcf brightnesses cxamplewould be the rearcnd of a truck. Most drivers but aremore casily damaged by abrasionand completely are knowledgeableol truck sizesand can estimate lose thcir reflectivity when wet. Ncwer versionsof distancesof trucksby virtueof that knowledgewhcn such encloricdbead matcrials, rel'erred to as encapsulatedlcns vehiclcsare well illuminated.On the other hand,when sheeting,have providcd higher brightncsse s while retaining trucks are poorly illuminatedat night, sizc cucs are prt)tectivecharactcrtstics. degradedand estimationsof distancewould bc expected With regardto prismatic-basedmaterials, the corner of to bc degradcdas well. a cubelorrns three mutually pcrpcndicular surfaces that In a lirboratorysetting, Jannsen(6) found that changes will rellectlight back in thc direction of incidcnce.This in sizeand brightnessoltaillights were inellective cucs in principleis usedin two typesof reflectornraterials: rigid the detcctionof relativcmotion in depth. His rcsults plirsticand sheetingol vinyl, polycarbonate,or other indicatedthal changesin theangular separation bctwccn plastic rrirterials,These reflectors arc typically brighter taillightsconstituted the prirnarycues for suchjudgmcnts, than bcadedglass materials at srnallobservation angles Suchlindings were confirnrcd in on-the-roadstudies(7.8). but exhibita sharpcrdecrease in brightnessas that anglc I n cxtrapolatinglrom theforegoing, it sccnsapparent incrcirses. that the perceptionol movementin depth would be A numberof conditionsrcduce the life expectancyof enhancedevcn more by presentinga largcr target to rctrorellective materiells.The top laycr ol' reflective driverrthan thatinherent in tu,otaillights. In I'act,Fisher sheetingcan be darlagedby abrasiondue to dust.sand, and Flall(5)presentcd cvidcnce that outliningthc entire etc.Oxidation and otherchernical reactions cirn aifect the rear cnd of a truck was more effectivcthan the simple top cDat,intcrnal layers, and adhesivebacking. Ultraviolet anglegenerated by two taillights.As notedpreviously, exposurccan cause hazing discolor and allectpropertics one must assumedriver inattentionundoubtedly con- of plastics,resins, and the adhesivebacking. Physical tributessubstantially to dcgradationsin the perccptual impact (and any i1exingor bending)and extremctem- process.It seemsclear, thcrelore,that attentionand peraturescan causecracking. Moisture can also affcct the subjectivejudgments can be enhancedby improving adhesivebacking and, if it pcnetratesinner layers,can pcrceptualsiles. degraderetro rcllectivity. Wcatherconditions can severely degrade retroreflector Iog, dustatrd sand, snow, dew, Analyze Retroreflectiveand Fluorescent matcrials.Rain, blou,inB and frost reduce brightnessby (l) attenuatingand Materials scatteringof the light pathsto and from thc rcflector,and (2) forming a degradingoptical surl'aceon the rcflcctLrr. Rcl'lectivematerials are obvior.rslyfar lesscostly than Ertrpiricaldata rcgarding the durability of rctro- lightingsysten)s and far moreeasily retrofitted to trucks reflective rnatcrialsis severelylinrited. lt is therelore a thorough to irnprove conspicuity.Therefore, anall'sis difficult to predict reflectorlil'etime in truck operations materials performcdto of rellective was determinctheir from availabledata. It would appcar,however, that 5 characteristics,particularly thcir cJ'i'ecIivenessand yearsrnay be a reasonableexpectation. durability.

Retroreflective M ateiials FluorescentMaterials

A retroreflectordirects most of thelight it reflects back Fluorescentpigments are organic substances containing along the linc ol'incidence,i,e,, back toward the light dycs gapablcof fluorescingin solid solution,e,g,, in a source.'lhus, the rctlectoris seenas brightestwhen the paint pigmentor resin binder.Such pigrncntsconvert ohserver'seye is closeto the light sourcc.Retroretlectors Iight I'romthe shorterwavelengths (violet, blue, grccn, inherentlyhave vcry narrow beam pattcrnswith respect and ycllow) to longer wavelengths. l he lluoresccnt

843 Expeimental Sofrty Vehicles

energyis addedto normally reflectedlight, resultingin an Six experimentswere conducted, In someca$ssr subjects eflectivercflcction thctor of 200to 300pcrcent, compared directly observedconspicuity trcatmentson an actual to 90 pcrccnt for a bright, nonrel'lcctivecolor. Scveral truck. In othercases, slides were taken ofan actualtruck manulacturersproduce sheeting materials that are both and subscqucntlyused in a laboratrlrysetting. In still fluorescentand retroreflective. other cases,slidcs were taken of mirriaturevehiclcs on a Studies on visibility and conspicuity of fluorescent I / 25 scaleroadway and subsequentlyused in a laboratory colors agrcethat suchcolors are much more easilyscen setting. than are nonflr.rorescentcolors. Fluorescent orange The I'irst experimentevaluated 45 rear end reflector appears to be the most conspicuous.Of particular treatments and compared them to conventionalcon- interest,especially when consideringapplication to day- figurationsspecificd by the U.S, FederalMoror Vehicle timc truck conspicuity,is the fact that fluoresccntcolors Salcty Standards.Designs outlining the entirc rear are found to hc more attcntion getting in peripheral perirneterand rnudflapswere found to be superiorto all vision than arc ordinary pigrnents. other designswith rcspectto conspic-uityand easeof Thc most seriousdrawback to thc use of fluorcscent detection. materialsis their limited lifetime with ultravioletexposurc. In thesecond experiment, l2 differentpattcrns involving Two yeals is a practicalmaximum in most outdoor styleand color wercplesented in pairson a testtruck to situations,and usefullifetimc can be as short as 3 to 6 sub.iectsat night. Alternating white/colorcd rectangles months. Therel'ctrc,applications to truck conspicuity werefound to besupcrior in termsof conspicuity,detail, appcar generallyimpractical. and visiblcdctail. The actualcolor was lessimportant. The third cxperimentreplicated the sccond expcriment during the day. Again, the alternatingwhite/colored Task 2: Designand EvaluateAugmented rectangledesign was superiorto the other designs.I he (Retrofit) and New Integrated Lighting actualcolor wasagain of'lesser importance exccpt when fluclrescentmaterials wcre used, and Reflector Systems 'I'he fourth expcrimentst udicd the effect of reflectorizcd patternson Task I demonstratedthat the rangeof possitrilitiesfor rearend distancejudgrnents.Scven pattcrns wcrc cnrployed.The dcsign improvedconspicuity systems wits vcry large and available havingthe perilncterof the the mudtlaps judgcd empirical data were inadequatefor selcctingthe bestof rearend and rcflectorizedwere to be than the most cost-elI'ectivcdesigns. Thcrefore, Task 2 consisted closestto subjects the other designs.lt was also found lower the of a seriesof experimcntsfor resolvingimportant issues that the reflectorizedarea, thc closerthe truck and screeningout mostof thepossible dcsign conligura* appeared. The tions.Prior to conductingthe experirncnts, the Iollowing fifth experiment evaluated partial-to-complete perimetcr of the designguidclines were estahlished for theaugmented and outlines rear and side of trucks and integrated conspicuity systems: comparedthcm to the conventionalconfiguration during r Truck marking and signalingsystems should be day and nighttime illumination levcls.For nighttime conditions, c-omplctcperimeter standardizedas much as possiblc across all truck the

signals around the rear and side rails was recommended.A U- The currentlyrequired intensity levels for truck shapedoutline of the mudflapswas also recommended, anclidcntil'ication lighting appcar aclcquate. However, a usinga 2in-widc stripeof white rctrorcllectivematerial. nrininrumarca requiretncntcrl l2in2should be retaincd A varietyof rctroreflectiveand rc{'lcctivematelials and for rear signals,and considerationshould bc given lor devicescan be used,including glass bead and prismatic- toward increasingthe minimum arearequirctlcnts type sheetingsand reflex rcflectors. It is considered front and sideturn signals.ln nddition,consideration brake, essential.howevcr, that retroreflcctormaterials bc her- shoukJbc given to a dr.ralintensity system to aciiust metically sealed,Also, reflex refl$qtorsshould be ol a prcsence,irnd turn signalsto differcntambient ctlnditions, clisperscdangle prism design so that a wide angular suchas day, night,and log. characteristicis obtained, Minimum and maximum SIA (SpecificIntensity per Prepare a Detailed Field Test PIan for the Area) were recolnmcnded,bascd on con- unit values AugmentedSystem siderationsof minimum intensitr,ne cessary for adcquate conspicuity,the effectsof tcmporarydegradation due to A detailedtest plan was preparcdI'or field testingthe dirt and grime and long-tertnweathcring, and of glare recornmendedaugmented system. Sample sizes' fleet potential. Thcse were 250 to 300 ctl/lx/ml and 500 cornpositions,candidatc lleets, exposure data' accident cd/ lx/ m?,respectively, for thc stripeoutlining thr: truck, ratcs.existing truck rnarkings,shol't- versus long-haul and 200cd/ lxl mzand 300 cd/ lx/ m2,respective ly, for the operations,cxperimental and control group ulittclllng, mudflap striPe. and nraterialsand installationcosts werc discussed and Detailed materials arrd installation cost analyseswere evaluatedin detail.Two thousandtrucks w$re recom- performed for the recotrtm$ndedretroreflsctive design nrendedfor the augmcntedsystem treatment, and a and partial conl'igurationssuch as rail only. partial rail' matched likc number was recollltrlcndcdtor a coutrol broken whole outline. The 198I estimatedcosts and group.A 24-rlonthclata collection pcriod was conside red rangedfrom a low of $34for the partialrail treatmentto a aclcquateto demotrstratesignificancc between thc groups high of $416tor the completeoutline treatment. at appropriatealpha and betacrror levels. As witl be notcdin the followingsection, I'unding was Design a New IntegratedConspicuity System insul'ficientIor field testingthe completeaugrrented for Original/ Equipment Manufacture svstem,i,c., lull sideand rearoutline.

perimeter outline reflectorizationdesign for the The the augntcntedsystem described above was alstl recommendcd Task 3: Conduct Field Test of for the integratedsystem. AugmentedSystem on SelectedTruck Two pairs of four lights eachwere recommendedfor Fleets the rearlighting system ol trucks.Each set oflights could be positioned horizontally or vertically on the lower cornersol' the truck. The outcr (horizontal)or lower SelectConspicuity Materials (vertical)lights representcd red presencc indicators. The 'fhe manu- next light representcdamber turn signals. inner Prismatic sheetingknown as Durabrite and (horizontal)or upper(vertical) two lightscomprised rcd facturcdby Avcry Intertratiotralwas selectcd Ior thefield brightness, brakelights. Thus. this design not only providesseparation test.This selcction was hased on four criteria: I)urabritemore of functions,colol and sizecoding are also involved' easeof installation,durability, and cost. In addition to the two conventionallyplaced amber closelysatisfied all four criteriathan othcr material$, thismatelial {)n turn signalsat the front of truck cabs,two additionalturn However,the cost to purchaseandinstall dcsign signalswere recommended on eachside o{'the truck, one 2.000 trucks according tLr the rcctimmended budget. mounted on the truck's cab and one mounted mit-lrvay specificationspresented in Task2 stillexceeded modified as alongthe bodYor trailer. Thereiore.the designspccilications wcre Amber (except I'or rearmost lights) side clearance follows. lights cvenlyspaced every (r to 8lt, includingthe corncrs' l'hc recommendeddesign was a 4in-widcstripe outlining stripewas werc recommencledalong eachsidc ol a truck beclor thc entircrear and sidcsof truck trailers.This thc cntire trailer.The rcarmostlights were recommencled to bered- reduceclto a 2in width. And, whilc outlining rail to All of the lights werealong or closcto a truck'srailing. rearol'trucks remained essential, only the side was cost Becauseol' the high-mountcdrellectorization, no .iusti- betreatcd with thc prismaticsheeting' l'hc tnaterials ficationwas seen lor high-rnountedlights, including the lbr cachvehiclc was $35. photometric currcntly requiredcotrvctrtional thrcc-light truck identi- As can be seenin Table l, the actual material closcly ap- fication bar. It was bclicved the rccommendeddesign characteristicsof the Durabrite 2. lt will also amply rlescribcdand identiliedvehiclcs as largetlucks. proachedthe valuesrecommended in'fask E xp erim ental Sqfety Veh icI es

Teble1 Recommendedmaximum and minimum SIA truck collisionsin the reflectorizedgroup with alpha values (upper) and durabrite actual values and beta crrols of l {tabledentrios are in candslas/1x,/m"l . 0 and .50,rcspectively. f)uring thc data collectionperiocl, accident report$ wereobtairred I'rom fleet records ObservationAngle on a quarterlybasis. At Entrance the end ol'eachquarter, the f'lccts'firasteraccident logs Angle were revicwedto identify all tr.ailersfor which accidents werc rcportsd in that per.iod.Reports I'or trailers in both 0.20 0.5" 0.20 0.50 the reflectorizedand controlgroups were obtainccl. -40 Flachac-cident was coded with r.espectto identifying 330-500 150-400 75_125 38-1oO information, prccrash 475 325 90 62 factors,and, very importantly,the 300 150- 75_ degreeto which conspicuitywas a likelycontributing 38_ 19_ 'l or 22O 82 42 16 causal.ivelitctor. he conspicuitlr1211n* c6ding u,as 450 75- g- 38- 1 9_ conductedin a double-blindsituation by 6142128 two highly expericnccdmotor vehiclesafety prof'cssionais. AII accidentswcre placed in one White Red./Btue 'l'he ol six classifications. first thret classificationswer.e othcr-vehicle_into_ truck accidentsan

Collect and Analyze Truck Accidentf)ata

The planneddata collectionperiod was 24 monthsand was initiatcd in the rniddleol' 1993.Appr.oxinrirtcly 3 months rcmainas of this writing. I'he24-month period and 2,000l,$hicles per group (actually2,0til per gnrup) wercsclected to providea sarnplcsize/ exposure suliicient Figure 1. Cumulative numbgr of struck trucks by to detecta l5 pcrccnt reductionin other vehiclc_into_ quarter for daylight and nighttime driving

846 Section4. Technical,Sessrons trucks consistentlybeing hit at a lower ratethan control Burger,W.J,, R..L.Smith, K. Ziedman,M.U. Mulhol- "lrnproved trucks.f)ata for two additionalquarters will ultirnatcly land, M.C. llardirles.atrd T..l . Sharkcy. be includedin thisgraph. but it appcafsunlikely that thc commcrcial vchicle conspicuityand signalling currenttrends will hc alteredsignificantly. systems,Task l: interimreport," Vector Entcrprises, The rclativelylarge dillerence in accidcntrates between lnc.. SantaMonicir. California. March l9ltl. '-Visual daytimeand nighttimedriving is easily cxplained by the 4. Cole. 8.1,., aspectsol road cngineering," fact that thetrucks were driven to a rrtuchgreatcr cxtent Proceedings(lth Conl'ercncc of the AustraliirnRoad during the day than at night. Ilowever,thc dif{erence RcsearchBoard, pp. 102-148,1972. "The betweenthe controland reflectorizedgroups during the 5. Fisher,A,.1., and R R Ilall, effectof presence day is not easilyexplained becausc thc rellectoriTation's light on thc detectionof'change of vchicleheadway," effectivcnessis primnrily dependenton tl-relight plojccted AustraliirnRoad Rcsearch,8, pp. l3-16,l97tt. "l from othcr vehicles'hcadlights. On the other hand,thc 6. Jannsen.W.H., hc pcrceptiott ol' maneuvcrsof red/white and red,'bluc pattcrns do increascthe conspic- moving vehicles:pcrceptability of relativesagittal uity ol truckssomewhat. Furthcr ar-rrrlyseswill herequired motion on the basistll'changcs in apparentsiz,e or to explainthis findingmore fully. brightnessof taillights,"Institute lor Perccption, In conclusion.thc l'ieldtest appearsstrongly to be Holland.1972. "The demonstrrtingthat increasingthe cotispicuitvof large ?. Jannsen.W,H., psfccptionof maneuversof trucks will reducesubstantially the number of other- moving vchicles:thresholds for relativemotion in 'l vehicle-into-truckaccidents. his findingis particularly dcpth." lnstitutefor Pcrception,llolland, 197-1. significant in vicw of the fact that the conspicuity 8. .fannscn,W.H . .1.A.Michon, and 1..().Harvey' "The treatmcntsemployed in this field testarc considerably perceptionof leadvchicle rllovclllent in dark- lessemphatic than wasrscorlmended.'l'wo-inch rather ness,",4r'r'irle nr Pret,tntionantl Anal.l'si.s,8, pp l5l- than4in-wide: stripe$ effcctively redrrccd the recommcnded 166.1976. "Sensitivity SIA valuesby 50 pet'cent.In addition"the use of rail-only 9. Smith, W.M., to apparentmovement in reflectorizationol'trailer sidcs eqrtally I'cduced the rccom- tlrpth as a lunction ol' stimulusdimensionality." 'l mendcdconspicuity. hus.thcrc is strong likclihood that Jotrrnal o.f FlxperimenlalPs);t'ltttlog.t', 43, pp. 149- c\,'engrcater rcductions of othcr-vehicle-into-truck l5-5.1952. "Effect accident$will occur with the recourmendedrellectori- l0 Smith. W.M., of monocular and binocular zation treatnlcnt. vision on the scnsitivit)'to apparellt lllovement ln " dept lr, Jrrur na I t1f E.rp er i til t'tt t d I P.s.r't'ln log.r',4 I. pp. 357-363.1955. "Perceived ll. Steedman,W.C., and C.A. Baker, move- References : ment irl depth as ir function ol stimulus size," AerospaceMcdical ItescarchLaboratory, Wright- '-Motorcycle l. llurg, A., and J. Beers, reflcclorization PattersonAir Forcellase, Ohio, 196l. " for rrighttimec,ons p icuity, University ol' Califo rnia 12. Zicdman,K., W.J. Burgcr,R.1.. Smith, M.U' Mul- "lrnprovcd Schoolof Iingineeringand AppliedScience I{eport, holland,and T.J. Sharkcy. commercial Los Angeles,(-alifornia. 197(r. vehicleconspicuity and signallingsystcns. Task II; "tticycle 2, Burg,A., and S,F. Ilulbert, wheelreflectori- analyscs,experitlctrts and design recotntnetrdation," zationas an airl to detectionand recognition."Los VectorEnterprises, lnc., SatrtaMonica, Calilornia, Angeles,California, 1976. October1981.

847 Experimental Safety Vehicles

The MVMA InvestigfltionInto the Complexitiesof HeavyTruck Splashand Spray Problem

Clarke B. Gorte little doubt that reductionsin driver visibility,regardless Ford Motor Company of reason(srrow, rain, fog, smoke,or vchiclesplash and spray), are important to the sale operation of a motor Ronald C. Joyner vehicle. GeneralMotors Corporation Splashand spray is not a new problem. Long before motor-driven vehicles,pedestrians and other vehicular Kjell Pedersen and equestriantraffic were confrontedwith thc splash InternationalHarvester Company and sprayannoyance factor. Motor vehiclescompounded thc public irritation in theearly days of soft roadsurfaces. Carl C. McConnell Ovcra periodof severalyears, driver vision was aided by windshieldwipers, fender dcsigns, and vehiclerludl)aps. Motor VehicleManufacturers Association MLr

848 Section4. Technical.Sessions results of these tests indicated that reduction device , NHTSA auspicesof severalspray attenuation combinations previously considercdcffcctive did not trcatments, using the samc itrstt'uurcntation and censistentlymakc a discriminatedifl'crcncc in sub.iective test sritup.and identicalvchiclc combinations' evaluations.Subsequcnt tests conducted by MVMA at (Note:l hc DOTi NH'I:iA datawcrcnotavailable thesame site also failed to find consistentimprovemcnts. l'orstatistical analysis Ior inclusionin thisrcport. In .lanuary1984, DOT/NtlTSA begananother series Theseconrparative studies will bc avnilableat a of testswith SystemsTechnology, Inc., as contractor at a laterdatc.) test site at F-ortStoc,kton. Texirs. 2. Test vchiclecombinations not includeclin the The methodologyused was substantially that developed DOT/NHISA tcst projectto determincto a earlierby David Weir( l), using objcctivelaser measure- , greatercxtcnt than would otherwiscbc possible 'l'hese ments. ltrll-scaletests were dcsignedto correlate whetherdillc'rcnt types havean clll'ct on the laboratorytcst ranking ofvarious types ol spraysuppres- cllicacyof sprayattenuation devices. sion dcvicesp11 various vehicleswith objectivelaser 3. l)cvclop new andl or Inorcextensive instrttmen' mca$urements.The resultsof this testproject are being tation that can provide more comprehensive, statisticallyanalyzed under MVMA sponsorship' cost-efTective,obiectivc meirsures of spray Irom In addition, MVMA has conductcdsttpplementary heavytrac'tor-t rai le r cotnbitratiott veh icles' tcstsduplicating the l'ort Stocktotrapproach as closell as 4. I)erfolmstatistical anetlyscs ol collectedtest data possible.Data frotrrttr$sc tcsts irre useful in filling gapsin for the purposeof cvaluatingheavy trr.rck splash the N TITSAdata and are considered important to lnsure and sprayattcnuation devices. that the devices requirements adoptcd irr future DOTiNHTSA rulemakingwould be practicableand Test Prepflration efl'ectivr..The balanccof this paper describesthc 1984 V M A splashand spray project and the test conclusions M Thc testing was carried out at the Tcxas A&M 'l'exas in detail. Univcrsity Transportationlnstitute (TTI )l Proving Groundsat Brvan.Tcxas. The ProvingCrounds, located air base,providcd the necessary7'0()0tt ProjectObjectives at an abandoncd -l-he runway f'ortcsting combination vehicles at 55mph. The purposeof this projectwas to devclopquantitative test arcir (Figure l) includctta new 400ft scctionof attcnuation asphaltsurface, constructcd on top ofexistingpavctnent, and subjectivcdata on the splashand spray 'l performanceof dil'lerentaerodynamic dcvices and spray to duplicatethe Fort Stocktonsurfhce. hc asphaltmix reductiondcvices applied to heavytractor-trailer com' wasde veloped to provirJea finalaverage tcxturc dcpt h of binationvehicles, I hc datacollectecl through this tcsting 0.-1-1in.I)uring constructiotr,cxtla care wits titkctrto pro.iectwould supplcmcntthe resultsof similartesting produceas levela surfaceas possibleto eliminatcwatcr conductedundcr the auspicesof I)O l/NI{TSA. I Ob.jectivesof this projectwere to- I'rincipal investigators:D.L, lvey. R..1.Koppa. O. Pendleton.and R.A' l. Validatc the testing performedunder DOT/ Zinnrer.

EtFrFlrEl llstacr

TIIT O'TIFVTE

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849 E xpe riment al Sof"ty Ve hicles

puddling. The new asphalt pavementwas designedto on an 8011X 4ft black backhoard50ft down thc vehicle have a I percentcross slopc over its t:ntir.c400fi length. pathfrom thecheckerboard. The three still cameras wers The width wasI Sftto allowfor a l2lt vchiclelanc ancl 6ft fircd simultaneously.by meansol'a pneumatic trip for rhe water to stabilize. switch as thc vehiclecombinirtion entered the testarea. All runs Surfacewater wa$ distributedto the pavementbv a werc recorded on video tape, and select runs were 4O0ft-long,4in-diamcter pipe. Warer wasdirccted to the recordcdon high-speedl6mm lllm. road surfaccthrough nin holes spaccd l2in apart to Eight low power lasers(5mw), located50ft from the provide unilorm wetting.Thc water supplypressure wa$ photo detectors or light meters in the checkcrboarcl adjustedthrough a rrranifokJand valve systento maintain targct, were usedto measurequantitativc 'I'o spravclensitv thc proper surfacewatcr r-lepth throughout testing. Water data, accountlilr crosswind,four lar".s werl located depth measurement$were recorclcd between cach tes( run syrnmetricallyon eachside of thevehicle lane. The lateral at l0 locationsspaced along 300ft of test surfacein the -fhc and verticalplacement is shown in Figur.e2. two whccl paths by the usc of NASA-type water rleprh klwerpositions are rspresentative ofeyc levels gauges.The in passenger watcr depth throughout the entire test cars, whilc the two highcr positionsare repr.esentativrof program was nominally 0.050to L).060in. eyelevels in pickupsand vans.The lower inboardlaser The maior clill'crcncesin this tcst project,as comparcd positions(numbers 4 and 7) rluplicatethe positions to prior tests,were the use used of eight lasersfor taking light in previoustest studies. transmissivitymeasurements and 35rnm photos simul_ All lasersand dctcctorswcre mountcd in waterprool taneouslyon both sidesof eachcombination vehicle as it enclosurcswith stablc mounts (Higure3). The siurdy went th|oughthe test arca ( FigureZ), An glt X l2ft black mountsdid not permitany rnotionof thelase r beamdue and white checkcrboarrltarget was positionerjon sach to air blastor pavcmentvibration, which side of the vehiclclane. couldproduce llawcddata. Trial testswere run to Perpendicular deterrni.eerrectivcness. to thetrack, l20ft from thecenterofthe An innovative lens systemwas deveklpedto locus the vehiclelanc, a 35rnmstill carnerawas f'ocusedirr a nolnt 0.75in spot at the detectorback to a pinpoint 'l'his on the lOrnm photoccll. tcchniquesliminrrtcd the signal noiseexpcrienced in pr.iorstuclies as a rcsultol'nonuni_ formity acrossthe beamin addition to beammotion due to air densitychangcs. Signalslrom thc detectorwere displayed on mctcrslor alignmentpurposcs and then transmitted to thetelcmetry system in the control trailer. The_sesignals were thcn relayed via rirdio to the basestation (Figure 4), These datawere then t'iltercd through a 5Hz, 4th orderlow pass I'iltcr(llutterworth). whichapproximatcs the reacrion of thc hr.rrnarr eyeto rapidlychanging densities (Figure 5). AItcr filtering, thesc data werc recordccion magnetlc Figure2. Test setup looking downrange tapc, a strip chart,and the digital computer.The strip

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Figure 3, Laser housings and photocell dst€ctors

850 Sect ion 4, Technic alIessrons

((l+{ tr Etotll |ESTfiEf,.l8 tfiral*n; rc oATE: itlrl' F""*l tiI)sPtED: 2r}H ffiGTEfr: llotEo l*b r-]r^*rt- I (8C|G$rl rfi rflsrilt lrr_l I rrru Ftttt i ! lottr 6rr'r rllI ri i "r,or (.rrr I I onr t'lsr I l*-'lrl r4 $rl -../to u* srrflo| Figure 7. Typical computer printout Figure 4. Therefore,in thistype ol testing.either a 50or 80ftlaser and detectorseparirtion could be used(l'igurc li). I hc c{'f'cctsot' wind. believedto be the most signilicant uncontrollahlc variablc. were minirnized by taking identicalrncasurements on both sidcsof thctcst itrcit and by runningthe comparative tcsts within 4 to 5min.Wind speedand directionwere measurcdprior to cach test usinga prccisionirnarnouletcl' antl I'ccordcdtltr a strtp chart.Tcsting limits were set at a maximumwind speed of lOmphallowing for gustsup to l2mph. Ambientair temperatrrrcand relativehumidity werc alsttrccttrded; howev'er,no data correctionswere deetrtccl ncccssitt-y.

Figure5.

chart providcd instantaneousanalysis of data quality, andthc digitalcomputer provided a srlnlnlaryprintout of the minimum light transmission(based on 0 to 100 t F percentcalibrations) from each laser.A typical strip rI chart traceof onc transmi$$omctcrchanncl is shownin Ei" Figurc 6, and a typicalcomputer printout is shlrwnin i !. Figure 7. F End-to-endlaser calibration (nominally within 2 percent t of the truc filtcr values) was irchicvcd hy inscrting precisionneutral dcnsity {'iltcls oI' 12.25. and 50 pcrccnt in eachbeam and obscrvingthe iligitaloutput values. TFAT*IAIIH I 5l'uaEt To accommoclirtethe greaterlength of thecombination at a hcight6in vehicle,the number6 laserwas relocatcd FigureL abovenumber 7 laserand at a distanceol 80lt from the dctcctor.Thirty-six runs werc madc with a corrclittion As statedprcviously, all testruns weremade at 55mph coelficientol'0.91 between the 50 and ll0lt laser positions. with the serrncdriver for all runs. Vehiclespccd wa$ measured irnd recorded for cach run by means of a

It standard law enforcettrcntradar unit mounted in a t vehiclcposilioned behind thc chcckcrboard.The vehicle I specrtdid not vary by morethan tlmph. tr[ E =T Er I t Test Plan $r fr I il To assurethat objective laser test measurementswere I v lf repeatablclrom one siteand onework crcwto another, a severalDOT/ N H I SA testswcre duplicated using two of altl4fallrr, tltg .s.ffi thr actual vchiclestested by DOTiNHI'SA, Rcfcr to Figure t) for 6X4-long noseconventional cab and single Figure 6. Typical strip chart trace van trailcr.

8sl Expeimental Safety Vehicle s

For this test study,the contractorwas requiredto use tions of side-mountedskirts, trcatcd (suppressant) flaps, three different cab types (COE, long and short convcn- and various aerodynamicdevices. Each of thesecon- tional cabs), three van trailer types (96in-widesingle, figurationswas repcirtedthree times Irll a total of l4l l02in-widesingle, and oneset ol 9(iin-widedoubles), arrd runs. Each run consistedof a calibrationvchicle com- two spraysuppressant type devices (rcar of axle-mounted bination,an untreatedbascline combination (idcntical to flapsand vchicleside-mounted skirts), See Figures 10, I I , thc testvehicle). and the treated test vehiclc combination and 12. (Figurc l3). Thc total numberof runs lol this program Out of the seriesof vehiclecombinations there were 47 was396. conl'igurations.These configurations incluclcd combina- The crrlibrationvehiclc combitration was equipped with ncw, plain, masticatedrubber llaps (at the trailer rearonly) mountedin thesame location as the suppressant flaps,The basclinevehicle combination (identical to thc testvehicle ) was also cquipped wilh new,plain rnasticated 'l'he I'laps(at thetrailer rear only). testvehicle cornbination reccivedvarying levels ofsuppressant devices as requiled by thc tcst matt'ix. Tlrc ploicct contractorconsidered skirts and suppres* santflaps (manufactured by SchlcgclCorp. and Monsanto Co.) to be representativeol the current state-of-the-art 'l'hese devices. deviceswerc installed in locationsrecom- mended by the devicc manuihcturer.No attemptswere madedurirrg this tcst pfogram to varythe locations ol the skirts or treatcdflaps. ljigure l4 showsa typicalIront steeringaxle skirtingarrd treated tlap installation.Figure l5 showsa typicaltrirctor drive axle installation (treated Figuro L Long nose conventional flap bchindlast axle ancl skirt noscof trailermounted). Figure l6 showsa typicaltrailer rear installation.

t.

Figure 10. COE with single v6n trailsr

Figure12. COEwith doubles

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852 Section4. Techntcdl,fesstons

fi,lii :,I!"'i1'r1;J testplan were designed to \.a4rq The specificobjectives of this producethe followingdircct ctltlparisons: l. Cornparcthc eIIect ol'aerodynamic devices a. Betweencab configurations tp- b. With various lcvclsof supPressantdevices 2, Compare the effectof supprcssantdcvices a, Betweencab configurations . b. With variouslevels of aero devices c. With plain masticatedllaps d. With varying lcvelsol valances

,,i$dl* "'fi;iibffff ,.#m*ft W "ttt i "lII ?lrpr Figure 14. $tser axl€ installation Trrctot Tr.lltl Sld. Sllrtr tvr $E{ljll !tl.rsr-{ !-9-S tr T! sL cot,6rt 5,-96' tr xtI tx, Co!. 6rr $V' t6' Ir ttt IT cot; 6ra 5v * 95: tr ITT t cDB, 6ta Ev - 96' Ir xxI Col, 6ra 8lt - 06' Ir T cOl, 611 51t- 96' T ttt TI CO!, 5ra EV - 16' I ttl TT cot, 6ra $/ - 96' t xtI I - ri rr|rifl'F COt, 6ta SV ta' r rtt ni ili{ lj,{q'r $ftqji:l1ilvxfr,rrl"'r' ft.41s!:rwlill{.,.l1}1 : COl, 6ra 8V - 9f: tlt CO!, 611 5v - 96' lll co!. 6ra 5/ - I0l' tr TTT ilf",*ry co!, 6ra 5v ' l0t' Ir TTI COe, dxl 5v - I02' x xxx CO!, 6xa 5V - lol' x XTT col. trl Dv - 96' t rlr co!. arl Dv - 96' I ITI Co!, rrt DV - t6' ITI COl' arl DV - t6' rxl

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Test Results To make somemcaningful comparisons of thc various treatments from these data, a method of pooling all The still photographicrecords of cachtest run as the measurementsfor the three runs of a unique setupwas vehicle reached the chec-kerboardrcfcrcnce surfaces used(see Figure l9). provrdeonly a qualitativefeel lor thc di{'fcrcnccsbetween the many vehicletreatments. Thc spr.aydensiry nreasure- lltt o il crLcujnla tlloll?[c mentsobtained d uringtesting provided the primary hasis IttI vrurtl fol evaluatingthe cl{'cctivcnessof the various spray 'l L.ft* iltiilar attenuationtrcatments. heresults ol thcscspra1,density l--il tl itr t tl measurementsare discussedin two parts as described lr .l lr rl below. l--1 fitl The first part of this sectionwill discussthe resultsof lr _.1 lrr-r rl the digitizedminimum light transrnissiondara for each t-d l--cl ilfr1 tl sensor1'or the testplan as follows; lr {l 17 rl l. I)atir reduction I and analysis 6tt+?r1-T-_ +frd fin+tr+td r.I (.'olrclation c/l|ql'r?tol 2. of sensormeasurements with one ltuFt (ln+h+Til ffa+t-+T1t..".'''T.---_ antltherand I with wind i r Pairlvisecorrelation analy,sis lffiT. r Pr.incipalcomponent analysis lr* lrl r Varianceattributable to testconditions I 3. f-'omparisonsttl'conditions by groupingor scrups 4. Analysisof varianccand other testsol'signifi- lffi l-rJr'a . cance r [)ifferenceanalysis of variance Figure19. r Regressionor covariatcanalysis of variance I Analysisof casestaken as trcatntents Geometric mean values Thc sccondpart willdiscussthe results ol'thc following were calculatedfor left and right specialcvaluations: sidclersers antl then combineclinto a third geometr.ic "Bol.h." nteanvalue expresscd as pooled rnsasuremerlrs l. The relationship betweenheavy vehicle speed werethus determinedl'or and the irmount of spraygenerirtecl eachset of threc runs per setup for the test vehiclcand the equivalent 2. Ohscrvcrlatirrgs of sprayclouds and correlation baselinevehicle. The baselinepooled with spraydensity mcasurements measurcrncntsare subtractcdfrom the testpooled measurcmcntsto providethe first indica_ tion ol how the vilrious vehicletreiltntcnt$ perform and compare. These data are presentedin a typical bar Data Reduction and Analysis histogram form showing thc differencerank orclered from lel'ttcr right in ascendingmagnitude for eachtype of The actual data recordedincluded eight readingsof vehicle(see Figure 20). minimumpcrccnt Iaser light transmission, wind velocity, and directionlor eachrun; the test(T) and baseline(B) vchiclcsarc idcntifiedand thesctup number that identifics FOOLED LASER READINGs BY sETUP TY?8. LNC o th SUE BAR CHART OF SUHS ,o I7.10 subdry July tt, 1984 thc specilic$pray suppressant lreirtrrcnt bcing eva]uated i (see to I Figure l8). I Note thereare thrce runs per uniqucsctup, that is, a l0 I ,o combination ol aeroaid,skirts, and spray flaps on the I I'rontstccring axlc and the tractorand trailerrear axles. r0 I o ,,," z4

trrloFr 5{$o.t ,rr!nr7 srrjot, rpu(i " e Ln(_' Figure 20. Typical rcs rE, Llu bar histogram chart rlr ,r{ Lsrj .t r .r Ljii: " LIL: The pooled measurementspermit some gross com- I I I11: parisons !t ' Lll: of thevarious vchicle treatments, However, clue LII: rq r to thc cffcct of wind directionsand velocity as well as limited data points, the contributionof eachlevel of Figure 18. Typical data sheet trealruentcould not bc evaluatedaccurately. Section 4, Technical .9essrbas

Correlation of SensorMeasurements

To further study the effect of wind direction and velocityon thc spraydensity, the useof eightdifl'erent sensorsin tlris tcst project permitted comparisonsof various sensormeasufements to determinccorrclatiort with oneanother in additionto wind effect. Earlier work hy Weir suggeststhat sensorslocated "NHTSA outboardof thc l-ocations,"i.e., sensors 4 and 7 in thistcst lrroject, provided littlc additionalinformation aboutthe spraycloud. As shownin Figurc21, a scricsof corrclationsof sensor4 versttssensors l, 2. and -j and sensor7 versussensors 5, 6, and tl werecomputcd bascd on data gatheredon the calibrationvehicle in which all eight laserswere operating. From this simplestatistical analysis,it canbe concluded that I'orcomparison purposes of one traatment versusanother, scnsots4 and 7 are sulllcient.

^dlutffi! n Y.l4' tod|lLrF !SIIJ!!II Figure 22. Pairwieecorrelatione among a€nsore Stifl a vr,

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s.nror 5 O,tt |,11 6l.a6l s.nrdf 6 0.7t z.lt ll.gn s.ilror 6 0.82 L96 t0.56t 5$ror t 1.00 1.00 35,8t1

Figure 21. Correlatlonof sensors4 and 7 with other sensors

' - " ''';i :'i ;'; il li ,-; ;; i: J; ii' A more in-depth investigationand analysis of the Figure 23. Baseline truck scatter plots-plot of sen5()t intcrrelationshipsamong the eight sensorsand wind 'l - sensor 2 sYmbol is vehicle tYPe effect werc conductcd using thc following statistical methods.

PairwiseCorrelation Analysis

Pairwisecorrelalion analysisis a bivariatestatistical procedurethat providesa two-dimensionaldescription of scnsorand wind relationship.Wind wasselected as a singleresponse variable representing both directionand spccd. Pairwisecorrelirtions were run amongall eightsensor readings,the wind cotnFonentfor the calihrationvchicle and the baselinevehiclc scparately. Thc rcsultstlf this in forrrtin Figure analysisare shown diagratttmatic 22. Figure 24. Baseline truck scatter plots-plot of sensor Tl picaldata plots for all scnsorpairs arc given in Figutcs 1-sensor 3 symbol is vehicle tYPe 23.24,25.and 26, The following observationscan be made concerning thesercsults: L Scnsorcorrelation patterns are distinctly dili'erent lincarcorrelations. Sensors 5 to 8 arenonlinearly for thc right sensor(5-8) ve rsus thc lcft licnsor related(see scatter plots shown in Figures23 (l-4). SensorsI to 4 have significantpositive through26).

855 E xp eri m ental Safety Ve hicle s

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Callbratron Vihicle

5a 5t 5l I $s 5o 5r 38 ltnd FEp. yr.

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6orh . l8 . ?r .36 .26 _.A -.t6 -, lt -.J' .31 ,6s Left -,4t -.44 ,,1t -,r! -,qZ .78 Rteht ..a6 -.$ _,{a -.a8 .40 .r8

Figure 27. Yehicle principal component results Figure ?5. Baseline truck scatter plot$-plot of sensor 5-sensor 6 symbol is vehicle type I. Right and lelt sensorsbehave oppositely as evidenced by the equal but opposite signed factor loadings when all sensorsare analyzed together. The $errsorsbehave oppositely with regard to wind; thc left sensorsare positivelycorrclated with wind and the right sensor$negatively correlatcd. For the purposes of comparing treatments, sensors4 and 7 are sufficient. 4. The brrsclinevehicle data did not reflect this behavior as clearly as the calibration vehicle data. Loadingson senriors2 anrl 4 werehieh for the secondlargest I'actor. Figure26. Baselinetruck scatterplots_plot of sensor 6-$ensor 7 symbol is vehicletype VarianceAttributable to TestConditions

Throughout the test program, a third vehicle. 2. Left sensors( I to 4) correlatepositively with the *'Calibration" the vehiclc:,was run with everypair wind cornponentand right sensors(5 to g) of evalua- tion vehiclcs.This vehicle was correlatencgatively. IIowever, thcse correlations equippedwith plain mudflaps behind the trailer rear axle as arcgcnclally lowcr fbr theinside sensor$ (2, 4. S. the only spray control device,and it wasleli unchangedIor 7). Thus. wind has the strongestef'lect on the theduration outer sens0rs. of the testing.Figure 28 pr.esentssummary statistics on this vehicle,spatially arranged to rel'lcctsensor arranse- menton thc chcckerboards,as seen down rang" PrincipalOomponent lnorti). Analysis Wind velocityand pcr.centagetransmission level standard deviationsare comparableto thosefor baselineand test This statisticalanalysis is a multivariiitc procedurethat vehicles.The sunrmary statisticsol' two categoriesof providcsa rnultidimcnsionaldescription of sensorand w,indrelation.ships. Sensor rcariings and win

856 Sectian4. Technical,Sesslons vehiclesare givenin Figures29 and 30,respectively. The to any standardtext on statisticsfor a further explanation dispcrsion in relationshipto each mean transrnrrrance, of inferentialtests, and the t-testor Z-tcst in particular. 'l'he which is expressedas the standarddeviation, is inclicative resultsof the t-testof meandift'erences betwccn all of the problem lacing all testersof splash and spray treatcd vchiclcs(T) and their baseline(B) vehiclesare devices:very largevariation. shownin Figure31. The large amount of variability in measurementsfor any givensensor is explained,at leastin part, by wind Ptot velocity and dircction, plus inherent variability in GFflt!d I 5Elsar YI'UE varrES 'lrl mcasurementsof a complex aerodynamicphcnomenon I lr5 a r0.3rl -6,n .@lr T I{{t a rt.t! suchas spray from a speedingve hicle. This variabilityfar I l|, I r|. ttl .t.$ .Hl{ lt0 I 50. exceeds that acceptablefor nrlrmal engineeringtcst t t lt protocol.It is this variancethat makesinterpretation of ^Im tl I ?', Ifi 4.tI .m0lF n^tE :l { lt.7al limited runs on a givcn configurirtiondifficult. rgl t, I r. dtl r,rt .04 mftE el r -9(n

lF rr tlfr tl I il. tl -l, ltt ,tl lll lrND vtroilrY . 6,55 |ffl Ir n tLEt rt I 2'.tl Sr^xoAnDDtvrAilfl . 1.70 I'IFH Rrxcr . 0 20 Ef TUILEI $ I '.Za 1.4 .22 ta. filltll J' , tr.a

Lttl R| 6rtT rSltntf lcrnt Dtff.r.rc. (Pr{0.0J} *rHtthIy Sttntftcr6E Dtlf.!.6E. (?r<0.001) ql.7t u I2.0 45.5 E 7?,6 ?l.ll ru 18.5 ?5,1 sD ?t { 9.51 xrx 6.q 5,I l?.5 95,8r mx 95.1 9/ .9 9S.I Figure 31, T-teet-esneors 4 end 7

27.5 lo.q ?2,1 57 0 ls.I tr.8 ?5.! lt,{ ].9 0 0 q,J For both l)OTi NHTSA sensors(and the othersas 91.? 86.0 sl,? 91,2 99,0 well), a significant diffcrcncc was obscrvcd. Ovcrall,

il nrt116. 5.0 transmittance\l'as more than twice as large for treated sl^s[D orvrAils'1,0 turcr I / vehicles as comparedto baseline.Sensor 4 had a mean valueof 10.38percent versus 25.33 percent for treated Figure 29. Summary $tatasticson all baseline vehicle trucks. That this great a mean value differencecould runs occur, and yet there was no ditferencebetween treated and baselincvehir:lcs irs mcasured by scnsor4, isassociatcd with a probability of' lcss than 0.00(lL l hcsc spray il Ltro YEtEtry . 6.55 lftl reductiondevices. taken ovcrall.do indeedwork. Srfio{r lkvfAil* . |.ft nH For the purposcof cvaluatingthe cffect la|cr . 0-15 of the cab roof-mountedirerodynamic shield on sprayreduction, (tfl ll6ilI thesetups shown in Figure32 were used. The t-test results 66,11 !I,E tz,t n 8!,i 2q,zl 25.9 ?5.0 rD ?t.{ lB,ll 6,J 9.6 ?l,8 9/. Jl ut r 98,c 98,/ s.6

t0.? s.6 7{,0 27.? ??.5 'I.t il., - {.9 0,t m.l r 5,8 rd |I' t lcl sJ.8 8c.5 97,6 99,, { at tl g .l It tt l| { t{ tl I t rl I at It la a It tt It u l! il tl I I tl I ll t Figure 30. Summary statistics on vehicle fl I ll I I ll I runs ll u u ll lt la l0 u t r| tl It Comparison of Conditions by Grouping of tf ,I I I t I Setups t f I I a I I It To cletermincin a generaloverall sense if thosc spray tl !l I T It tl reductiondevices cvaluated really work or areof benef'it. I tl tl It a statisticalanalysis was made using the t-test of indepen- I ll il I dent rneans.Tltis approach to infercntialstatistical I 'l'he analysisallows a gross kind of corrrparisonsetup. t-tsst for most of the samplcsizes of this test project 'l'he Figure32, Setup partitioningfor comparisonof condi- approximatesa Z-distribution-test. readeris ref'erred tions

857 Exp erim entuI Sa-fety V e hicle asshown in Figure3l, AERO versusNO AERO, indicate ctsl rflttlr ^tD $Ett OTIYC iltl the ditferenceson the left side(sensor 4) wcresignificant, I r, 3t I F F I but lessso on the right side.Il poolcd,these dit'ferences 2 ., t, zt t J F 0 would remain significantbeyond the 0.05level; hence, it I l. lr t F FI 3 can be concluded that thc cab-mountedaeroaid has a I l, I, tt t FI FT t measurableel'l'cct on reducing spray. Figure 32 also t la,lt*?l,tlill 0 I F 0 providesthe rcsultsof the comparisonol' spray levels 6 It,lt,15,lt 0 FI f$ I between96in-rvide and lO2in-widctrailcrs and indicates 7 It,22.ll,.t I I I I I ro.rt,rr,tt,tt,r3,la I ] l 0 no significantnrcasurable difference. I r r ,2t ,lr ,aa I j f3 t The abovelirrdings mcrely scratch the surfaceso far as t0 r.e,r.,zd;:t.Jo I FI F3 I making definitive statementsahout the many treatment stratcgiestcstcd,'l'-tests betwccn diffcrcnt individual treatrnentswith only three runs pcr trcatment or setup worrldbc unproductive,and, in any case,multiple t-tests for data that could be analyzedby morc sophisticated Figure 33. Setups classifisdinto 10 cases methodscan be very misleading. 'l hereforc,analysis ofcovariancc using several different Since,as Figulc 33 shows,the I'ew cases of flapsonly at modelswas performed on allthc datagathered for B and the rear covaried with the prcsenceor abscnceof an 'l'his T vehicles in this reseirrchproject. analysis is aeroaidand combinationsof'Steer and Drivc. this factor explainedand interpretedin the following section. couldnot beextracted indcpcndently. Thus, this analysis cor)cenlrateson dilTerenccsamong the variorrs combina- tions of Acro, Steer,and Drivc. l wo approacheswere Analysis of Variance and Othcr Tests of used.In the first, thc differencebetwecn test and baseline Significance vehicle sensor readings on equivalent runs was the dependentor criterionvaliable. l he othcr involveda Individuals$tupswere tested only threetimesl thcrcfore, more direct approachl'or controllingthe troublesome mcaningfulstatistical cornparison of transmissometer interveningvariableof wind.The firstanalysis is referred data is difficult. A strategy was devcloped to make to as the differenceanalvsis. inferencesconcerning the effectsol' diffcrent treatnent corlbinationsof'flaps, skirts. and aeroaid.This stratcgy DifferenceAnalysis of Variance rcquilcdthe saclificeof certainvariables, namcly. trailer type (which has bcen found to produce no signil'icant A two-factor interaction analysisof variancemodel dil'lerence)and tractor type (l'ive diffcrent tractors). was used with Acro and SteerlDrive being the main 'l'hese datawere simply collapsed over thesc two variables. effectswith three levelscach. This resultedin a missing Onccthis wasaccotnplished. a variable called Ae ro can cell design,since no Aero = [J and Steer/priug= (F-S) 'l'he be identiliedas havingthree levels: combinationor lcvclswere observcd. assumptionin No aeroaidinstalled thisexperimental dcsign is that the testand basevehicle Standardaeroaid experiencedsimilar wind conditions,Since this was Special(Celco) acroaid = $ preciselythe purposeol runninghaseline and test vehicles Anothcr valiableis the treatmenton thesteerilts axle in clusc $cqucllcc,this may not be an unrcasonable of the testvehicle, which can be calledSteer: assumptlon. Flapsonly Ilased on the considerationsof relationshipsamong Flaps and skirts =FS thc cight scnriorspreviously discussed.lbur different A third variablc is the treatment on thcdrive axle(s) of criteriorrvaria bles we lc dcveloped.Each variable requiled 'I-hese the tractor,which hastwo lcvcls,iustas the Stccrvariable a scparateanalysis oi vitriancc. variahleswere as does.This third variablcis calledDrive. follows (each observation is a differcnce between a A final variableis Rear,which is the rear (trailer)axle sensor's readings on a haseline truck pass and the treatment. Sinceall setupsspecified special llaps on the equivalcnttcst truck passnontcnts later): rear of the trailer, thc two levelsol'this variableare - r Variable I -Thc geometric mean of all F'lapsonly SCNSOTS Skirtsand flaps = g Variable 2*Thc geometricmean of sensors4 Figure 33 identil'icsl0 differentcombinations of these and 7 only variablesthat werctcsted in Ihcsctups of thetest rnatrix. Variable3-The geometricmean of left sensor$ Eachsetup, in otherwords, can be classified as being one only (l to 4) ol'thesctwe cases.In Figurc33, each ol'the l0 casesis Variablc4-The geometricmean of right sensors relatcdto thc sctupsthirt rnatchthat case. only (5 to 8)

858 S eetion4. Technical.fesslozs

The geometric rneanis frequency uscdas the measure sameaxles. Note in this tabl€that the interactionbetween of centraltendency when the randornvariable of intercst the levelsof aeroaidtrsirtntcllt and axle trearmentsls is a portion or percentsince thc population (requency unifbrmly nonsigni{icirnt,I'his meansthlrt whethsr or not distributionof suchrandom variable tends to beskcwcd. an aeroaid is installed has no differential el'l'ccton the The l'rcquencydistrihution of thesensor arithmetic mean efficacyof the wheel treatments;the pcrccntagechange did show a definjteskewness. The l'requcncydistribution (in this caseimprovement), associated with the useof an of thegeornctric rnean, on theother hand, appeared to be aeroaid,works as a constitnton whethcrwheel tfeatment nearlynornially distributed. To lurrhcrsr.rpport the use of is installed.lt shouldbe noredthat thc standardaeroaid geometricmean, analyses were run usingboth measures, condition occurredwith greaterlrequcncy in this data arithmctic and gcomctric,and therewere no dilTerences set;i.e., there were 63 standardaeroaid runs as comrrirred in rcsultsconcerning trcatrncltt effects. to 30 specialand27 nonacroconditions. Figure 34 providesa surrmaryof the resultsof this dil{erence analysis ol variance for. all four criterion Regressionor CovariateAnalysis variables,ln thistable, an astcrisk(*) indicatesa levelof of Variance significanceof' 0,05 under a null hl,pothcsisol' "no To addressmore directly the effectsof wind, dilference."'l'his signifies that n"reansthat ar.c as far.apart a second method of analvsiswas undertakcn,with the dependent in valuc as thoseobserved, among the variouslevels of or criterionvariables being thc transmissometer readings the factors beinganalyzcd, have a chanceof 5 in 100of for ba.selineand lest vehiclesconsidered separatell'. In being just that-chance-rather than retlectinga real this anirlysis,the crosswindvector component of wind is difference bctween treatments or cornbinationso1' enteredas independent just treatments" an variable liketrcarme nrs on the test vehicles.Other independentvirriables in the model werc, ari before, Aero and Steer/f)rive axle 'l'his CFtt "lil lat{|b|. combinations. modelessentially fits separatelinear I t a regressionlines Ior the four ways trlr t of poolingsensor data used in the dill'c'renceanalysis for each factor level rl a J a blr combination and tcsts fol the equalityof slopesand ftr/Ftrttl.l.' intercepts.Since baselinevehicles had no treatntents, t.|rt lt|;/Hil r.I.l I't. r.l. l'1. thcsclines should be equalin slopcand intercept.lf the slopes are cqual fol test vehicles, this implies that | rr.rP n.r 2r.l zl.a Xf! treatment cornbinationsshown in Figure 33 can be t H.tt f ,f ||.t la.f 0 ll.lr t.l r.t t.l cornparcdat any wind valuc and rcsult in the sarne conclusions.lf, horvever,slopes are not cqual, this findingwould suggc'itthat a treatment 3tr/Hil rtJl ll'0 r0.r r0.r il.r wasbetter under t.tl rt.l rt.f l|.1 a.l some wind conditiorrsthan undcr othcrs,lnequality of 7.t lt.l u.l lt.l l t.l intcrceptsmeirns that the treirtmcnt$werc not equalwith regard to the amount ol'spray rccor.dcd,and thus trOtlt t l. rrO,il dil'lerenttreatrnents can be rank ordcr.cclwith respectto Z. r.t. . l0l tlcrltlC^rt thc extentol spraycontrol. 1. c.orrBtlt r.rr lr !l!I$I!!gl Figure J5 summarizesthe findings of these Patcart tSalralttllc.r l.rc analyses, rl lrtrlllt lrblcl. organizcd as hcfore with lcspect to the four different

Figure34. Resultsof differenceanalysis of varianceon aero and drive steer comparisons

The rowsunder the significancematrix helpthe reader understandthe meaningol' theseI'indings. lior. cr.itcrion variable l, in which all eight sensorsare poolcd, a standardacroaid, across the board. produces consistently better results(a highcr maantransmittance difference of 27.I percent)than either the specialacroaid or no aeroaid.

The Steer/Drive combinationsare consistcntfor all rr.brtrstrt..ir rd.r fDtd ir Crlt.rld rrrr.Dt. hrlflirs but variable 3, as can be seenin Figure -i4. Thc niost effectivecombination is both flapsand skirtsfbr all rrxles, Figure 35. Results of regressionanalysis of variance on and it is signilicantlybette r than just flapsalone on these aero and drivs steer combination Experimental Sofrty Vehicles methodsof pooling sensorobservations. Bascline vehicle gconretricmean readingsare trlsoincludtd in this tnble Crltrrlon Yrriabllt l { for comparisonwith testvehiclc gcomctlic means.

ln this analysis,wind is not a significantcovariate ldr: Flrpr I Sllrtt 49.9 zt.6 50,4 89.5 either by itscll or in interactionwith other factors lor Flror QI{.Y 21.4 35,9 8t.4 critcrion variableI or lor variable2. I'hese,it will be remcmbcrcd,are (l) lascrrcadings pooled over all eight sensors,and (2) sensors4 and 7 only pooled by taking their geometricmean. ln the sectionCorrelatitln of Figure 36. Resultsof regressionanalysis of varianceon rear axleg SensorMeasurements, thc correlationalanalysis of sensor effects of skins on readingswith wind for thc basclincand calibration vehicle runs. it was determirredthat scnsersotr the left tak$n as an individual treatmcnt. Through analysis of and right correlatedopposite ly with wind; hence,the fact variance mctheds and criterion variablesidentical to that wind is not a signil'icantcovariate for sensorreadings those describedin the previous section, it should be pooled on both sides of the vehicle should not be possihleto make someovcrilll statementsconcerning the surprising.'[hat wind (really thc ct'osswitrdvector) relativccfficacy ofthese generic installations on vehicles. should be a significantvariable lbr clitelion variables3 In addition,an analysisof covariancewas pcrformed on and 4 is alsonot surprising,since thesc alc left-onlyand thesedata. right-only scnsorsrrespectively. Tl'rcsc gcometric means Ii igure37 summarizespooled laser readings for the l0 wcrcglcatly inf'lr.rcnced by wind velrrciticsand directions cases,plus poolcd case readings lor thcir equivalent from one periodol timc to another,and thus wind is a baseline vehicle runs. J'he pooled transmirt$ometer signil'icantcovariatc. This relationshipwas, howevcr, thc variablesare ( I ) thegeomctlic rneans of all eightscnsors, same for all factor Ievels as cvidenced by the lack of and (2) thegeometric mean ol'sensors 4 and 7 only,just as interactionof wind with rrnyof thesefactors. before.A studyof this tahlcwill showsome diflcrcnces The slopesand intcrceptsof the linesfor all lhctor lcvcl among tl-revarious cascs,and a quite evident overall combinations of thc baselinevehicles werc cqual, supcriorityof testvehicles over theirequivalcnt baselines. indicatingthat the baselinevehiclcs'pooled laser readings wereessentially equivalent for all runs. Thc rcsultsIor thc tcstvehicle responses, as summarized Vrrlrblar z in Figure 35, show that wind was a significantcovariate Cordltlont for the right and left responses,critcrion variables3 and 0rlvr Plar B T I t.9 4, but thc slopesol'thc regressionlines were thc sarnefbr ISFFS39.6r 29,f v.? ll t all lactor levels.Thus, equivalcnt conclrrsiotrs regarding ?9FFO49.9 Jl.l 2t.9 ra.5 treatrrlenteffectiveness will rcsultat anywind condition. !5FFS536.4 34.6 14.2 12.3 This figure againshows that Ior critcrionvariables I and .5FSFSFS5t.3 1r.4 ?8.8 ll,l 2, the standardaeroaid was superiorto eitherthe special 50FF0il.1 26.5 16.I aeroor no aeroaid. 60ttrt51t,l 24.0 23,t l t.9 When left'only sensor3 and right-only sensor4 are TlFFstt 6 28,r 8.8 14.5 ?5.4 8.9 uscd as the dependcntvariable, the resultsarc not as 8lFF0 ?1.2 31.9 8,6 straightlorward.For the right-onlysensors, there was a elFFts54,3 ?6.3 5t. I 24.0 J5.0 8.8 significantinteraction betwecn the kind ofaeroaid treat- lolF5FSS ment that was uscd and the wheeltrcatrncnt used. The main ettecls ol wheel tlcatrnentclosely parallel the Figure 37. Summary of pooled laser readingeby cades findings o{ the dilfercnccanalysis of variancc;the fuller the treatmentof tractor irxlcs.thc better the results. The following methods of analysis were uscd to As a supplementaryanalysis, the singlcfactor of rear determinetreatment cffects: axle (on the trailer)with two lcvcls flapsonly vcrsus L Analysisol Dillcrences-Inwhichthedependent skirts and flaps-was studied,using test vehicledatrt variable was the diffcrcnce in laser readings, only, The rcsultsshow a signil'icantdifference between sensor by sensor, between the test and the thesetwo conditionsfor all but the right-only$cnsors, baseline vehicle on a given run. A one-way with skirtsand flapssupcrior to llaps only on the rear analysisof varianceand a duncanmultiple rrrngc axles(see Figure 36). test werc run r.rsingl0 casesas the indeperrdcnt variable(each case is a levelin thisfixed model). Analysis of CasesTaken fls Treatments f)ata wereanalyzed by separatewind directions A dillerencreapproach can be takcn for thedata of this dcfincd as either a positive or negativevaluc study,ifcach ofthe l0 casesidentified in Figure33 can hc accordinc to the crosswind vectclr. Another

860 Sectlon4. Technical Sessions

analysiswas performed with only thoseobserva- Thesefindings can be intcrpreted as follows. Cases10, tions in which a crosswindcomponcnt of equal 9,and 7 wereuniformly superior across all winddilections to or lessthan t2mph wasrccorded ("no wind"). and typesof poolingof laserreadings. C'ases 3 and 5 were RegressionAnalysis-Which is similar in ap- generallyleast effective in attenuatingspray. proach to thc diffelences analysesdiscussed Turning to an analysisoi' individual sensordata, earlierand yieldslittlc more definitiveinforma- Figure 39 providesrank order infbrmation.Treatmcnt tion. A scparateregression linc was dcvcloped diffcrenceresponses thart are underlinedare signiticantly for each of the l0 treatment combinations different than those that are not underlined and are (cases).These regression lines were then compared signilicantlygreater than zero. Cases l0 and7 againwere for equality of slopeand intercept. consistentlyselected, although case 2 wasrankcd as one 3. Analysis o[ Covariance- In the analysisof co- of the besttreatments by sensorsI through4 but not by varianceregression, model wind wasconsidered sensor$5 through{.|. Convcrscly, case 4 wasranked very by fitting linesfor pooled laserreadings versus highly by sensors5 through I but not by sensorsI wind (crQsswindvector) for l0 test casesand through 4. theirequivalcnt baseline runs. Hence, 20 lines of regrcssionwcrc fitted simultaneouslyand then testsdby cqualityof slopesand intercepts.Since (lndlvldurl 5rnrorr: ) this procedulc involved multiple hypothesis 5l 629tlr365 g 4 tcsting(40 paramete rs bcing estimated), in order s2 t l0 6 9 sl r+-1 2 rd I I | 3 I 6 5 to have an ovcrall significance(s) levelof 0.05 5a l2r-06991511 for rejectingthe null hl pothcsisof"no significant s5 ! e l,__8 !! f I ? I J r l0 I l { 8 6 Z 5 J and were dil'lerence,"individual slopes intcrcepts st q 4 I l0 | 6 I I ? 5 tsstedat thc lcvelof 0.00l. st 7 g r0 4 I f I Z 5 I Criterion variables used in these analyseswere the usualfour descrihedpreviously, plus a specialcatcgory Figuro 39. Rank order of casesby indlvidualsensorc consistingof eachsensor taken individually (no sumrnary by pooling).Duncan multiple range tests were then used of and to evaluatethe significantdifferences found amongmany In summary, a standard full treatment flaps with aeroaid of the I 0 cascsin thc diffcrcnceanalysis. skirts on every axle, together a standard liigurc -38identif ics cascs in rank ordcr of efficacyin (case l0), providcd the best overall results in spray Leavingthe stecring axlc withoutskirts but attcnuatingspray from leftto rightfor criterionvariables attenuation. else(case 9) isnext most eflicacious, l, 2, 3, and 4. J'hose cases identified in each row installingeverything "All are retainedonly correspondingto an analysis such as Winds followed by a treatrqentin which skirts (considered)"arc citscssignificantly hctter than thcir on the rearof the trailer.Case 2. whichhas no skirtsbut addition to a specialcab baselineequivalents but not dil'l'ering signil'icantlyamong does have cab side fairings in produces wind-dependent themsclves.Case rrunrbers in parenthesisare casesthat rool'mountcd aeroaid, highly critical, since the cases mark thethreshold from significantlybetter than baseto eflccts. The aeroaid is very perform to poorly (cases5 and 6). no better than base(itt someinstatrces worse). without it erratically

RelationshipBetween Speed and ^llllrdrr I094 7 t 86 I l(l) I ctndr: l0 9 7 4 I I 6 I 1 (t) Spray Generated x.5tl. Ytnd: lo 4 t 6 I i ? I I (1, Slg. Htndr l0 9 6 4 I 7 r t 5 (!)

Slt, Hlnd: 9 2lO 7 a I I 6 I (5) Hlftdr I I o I (!t I, I ll0 t. Specialspe e d tests(in incrementsof 5mph from 35 to ri't'il'r I rc trern of l,*l I $"n llroErrrlr Hlrtr ol RlBrr sdnrnri(5-8 60mph)were conducted using various levels ol suppressant I !lnJir: I 710 I A | 4 AII Plndir: i 9lr) / I t 6 I 1 (Jl devicesand plain rubberflaps. lt can be concludedthat Figure 38, Rank order of cases speedand spraygeneration are linear and thatcombina- tion vehiclespeeds over 60mph will produceunacceptably high levelsof spray. In Figurc 38, first resultsare shown for all data (all winds)for variablesI and 2. Thcn resultsby comparing data gencratedunder ltlw rtr no wind vcrsuiisignificant ObserverRatings and Correlationto Objective wind arc given.For left-only and light-only scnstrrdata, Measurements wheredirectionality is obviouslyol interest,rankings of casesare shown for theall windsconsidered analysis (all To bettercorrelate observer ratings and objectivelaser winds)and for only thoseobscrvations in whichwind is measurcmcnts.the relationship betweenspray density significant(greatcr than f 2mph, crosswindvcctor). and observcrcontra$tscnsitivity was ini'cstigatcd.'l'o this

861 Ex p erimental Safety Ve hicle s

end, a vision contrast test systemmarketed by Vistech to define the hardware requirementsfor potential field Consultants,Inc., was uscd along with an artiijcial implcmcntation. rainrlakcr.Observers. plus a single laserbeam, were used l he gencrationand useofan expantlcdlnser beam up to rate ler,'els Iour of transmission;100 pcrcent (no water), to 6in in diameterwclc slrownto be simpleand straight_ 60 percent, 40 percent, and 20 percent. Prcdicterbly, forward.Beams l2 to l5in in diametercould also be e asy contrerstdiscrimination falls off rapidly with increased to generateand apply. By virtue of averagingover a densityol sprayor as the Iincncss ofthe targetpatterns larger area of thc spray field, the expandcdlaser beam increases.An evaluationrrf'thc computedpercent change arrangernentmay provide a usef'ulcnhancement ot'the in contrast sensitivityol thc lascr comparedto observer lasertransmissometer scheme. Thus, field evaluationof ratingsdemonstrated a high degreeof correlation(.92). the expanded laser beam transmissometerappears Basedon thcscf indings when a conditionol 40 pcrcent worthwhile. lasertransmittance was reached,obscrvcr contrastdis- Photornetermeasurements of the light scatteredas a crimination had tallen oft by a lirctor approachingtwo. beamof light passesthrough thc sprayfield do not appear It can be concluded that when sprayobscures light to to havepractical application for measuringthe visibility below40 pcrccnttransm issivity, Iossol' ohscrver contrast throughthe entirespray f ield along the side ol'a vchicle. sensitivityrcsults. Such a controlled test docs not re- A photometerfocused on thc bcarnwould receivcpower producethe dynamicsituation of a driverrrttempting to florn only a srnallarea of the spra_yfielcl. H owever.such pass a truck with all ol' the variablesof winrl, spccd, methodscould provide a usefulmeasurement oi'local aerodynamiceffects, windshicld, windshield wtpers, erc. spra.ydcnsity. Therefore,a conclusionthat treatcdvchicles mustachieve In a scatteredlight-measuring systcm, the light level a thresholdlevel of 40 perccntor.above for the motoring rcccivcdhy the photometeris sever.al orders ol'magnitude public to perceiveimprove rlcnt cannot be substantiatccl. lessthan receivedin a tran$missivity-measuringsystem. Llonsequently,a modulaterjlight ,$ourceand a scnsitive bandpass-tunedphotom!'ter must Innovative Instrumentation be uscclto detectthe scatteredlight separatelyfrom theambientlight. Usinga l0mW laserlight source!with 100perccnt modulation, a Within the scope of the rcscarch obiectivcsof this tuned photometer with a scnsitivityof at least50pW is project, the Univcrsity of Micliigan Transportation requilcd. Of course,a lesssensitivs photometer would be ResearchInstitute (UMl'RI) corrducrcda limite

662 Section 4. Technical,Sessrons

Any improvement varied with vehicle/trailer Expanded laser beam transmissometers,up to configuration arrd,depcnding on baselineper- lSin in dianreter.appear fcasibleand allow formance,improvement can beexpected but not spatialaveraging that will reduccrcceived output quantitativelyprcdicted. fluctuationscaused by largewater droplets. The relationship between vehicle speed and Photometermeasurrj ments of scatteredlight are spray densityis an approximatelylincar one. feasiblefor measuringlocalized spray density Above 60nrph,the efl'ectiveness of any treatment but not throughout the entirespray field. was totally negated. No correlirtionmethodology or procedureexists Insufficient replicationsof treatmentcomhina- to relatethe improvementin light transmissivity tions were made to permit adcquatestatistical to imploved visibility as perceivedby the analysisof the relativccontribution of specilic motoring puhlic. treatlnentsat various locationsor the effcct of LJndercontrollcd conditions. the contrast sensi- wind condition on treatmenteffects. tivity of an observeris substantiallyimpaired when a lasertransmissivity af belor,l'40 percent through a Fpraycloud is reached. Equipment/Procedure References r I Computer image digitization of spray cloud "Red density appears to be a viable alternative to l. Weir, D. H., etal., uctionof adverseaerodynamic costly and stationarylaser instrumentation. effects of large trucks," U.S. Department of r Use of eight lasersversus two provided little TransportationReport, FH WA-RD-79-84,Septem- additionalinformation ahout the spraycloud. bcr 1978.

An Evaluation of the Obstacle-AvoidanceCapabilities of ArticulatedCommercial Vehicles

Paul S. Fnncher The purpose of this paper is to describeanalytical The Universityof MichiganTransportation approachesused for cvaluatingthe stecring and braking Researchlnstitute perlormanceol hcavytrucks in a currentprojcct sponsored by the NationalHighway Traffic Sal'ety Administration (NI'ITSAXI) in the [JnitedStatcs. ln that project,the sensitivitl,of vehicleperforrnance to paramctricchanges Abstract in component characteristicswill be evaluated.An ultimatc goal o{ thc N H'l SA projectis a vehicledynamics 'I'he Analytical methods are used to evaluatethe braking handbook for straightand articulatedheavy trucks. and steeringperlrlrrrrance of tractor-scrnitrailer,truck- approach describedwill he used in lornrulatingthe full trailer, double.and triple coruhinationsthat have vehicledynamics handbook. mechnical properties correspondingto current desigrr and usagepractices in the l-lnitedSrates. Description of the Methodology Introduction The results presentedare basedon models developed I)riversof articulaledcornmercial vehiclcs are expecled during studiessupported by the Motor VehicleManu- to stabilizedirectional responss, avoid rollover, and facturersAssociation (MVMA). thc FederalHighway judge stopping capabilitiesunder various operating Administration(FHWA), the State of Michigan,and 'I 'l'able conditions. his paper sxaminesthe extcnt to which the NH l'SA. I provides correspondenccbetween design and configuration of, combination vehiclesin- open-loopvehicle maneuvcrs, colnputerized models, and fluence( l ) thenature ol thcdrivcr's control tasks, and (2) publishedrcfcrcnces. Simulated vchicle maneuvers have the fraction of the tire-road friction that can be r.rsedin becn usEdto make designevaluations similar to those succcssfullyavoiding obstaclesand resolving traffic that might have been obtaincd from typical vehicle conflicts. resrs.(19,20,21).

863 Experimental Sqfety Vehicles

Table L Correspondencebetween models,references, and maneuvers

Models BackgroundReferences- I 1. StaticRotl 12,B) Equilibrium Analyses 2. High-speedTracking (4,5, 6)

3. SteadyTurning (Handling) (7,8, 9, 6)

4. ConstantDeceleration Braking (10)

5, Low-speedTracking (Tractrix) (11, t 2, 13)

6. LinearYaw PlaneAnalysis (14,t 5, 5) Simulations 7. Yaw and Roll(Constant (2, 10) Velocity) ,|7, 8. ComprehensiveBraking (16, 18) andSteering

* Simplifiedversions of rnoddlsI through5 havebeen developed in (11.

- Maneuverst2345678

Steady Turning a.Roll X X X b.Tracking X X X c.Handling X X X

Straight-LineBraking X X (ConstantDeceleration Braking) l

Low-SpeedCornering X X X (ln-Town Corner)

TransientTurning X X X (Ramp-StepSteer)

Obstacle Evasion XXX

Responseto ExternalDisturbances XX

Braking6-^r-!-^ ini- a^ Turnf..-^ X

For most of the maneuversemployed here, a perl'orm- A family of maneuversand associatedperformance ancesignature is obtainedfor cachtype of vehicle.l'hen, measures(see Table 2) hasbeen selected for assessingthe performancc measuresare evaluatcdat safety-relevant inllucnces of changesin vehicle properticson steering levels oi' the perlormancc signaturesof thc various and braking performance(I ). The steady-turningmancu- vehicles.For example,in a steady-turningmaneuver. the ver is used to examine three aspect$of performance, roll angles of the vehicle'sunit increaseas the lateral namely,roll, tracking,and handling.Constant decelera- accelerationof theturn increases.At thelimit of perform- tion braking is usedto evaluatefriction utilization and ancs, enc of the vehicle'sunits rolls over at a level of brakirrgefficiency, The other maneuver$are transient in lateral accelerationcalled the rollover thrcshold. In this naturc in that thcy involve changingfrom one path to case,the roll angleversus lateral acceleration graph is the another. performancesignature and the rollover thresholdis the Some of the maneuversare open loop suchthat a test $afctv-relevantDerformance measure. driver would perform predeterminedcontrol actions Section 4. Technical ,Sessrons

Table 2. Performance signatures afid msa$uresfor various manauvsrg

Performance Sig natu res Maneuvers (or OperatingCondition) PerformancaMeasures Steady Turning a. Boll Lateralacceleration Rolloverthreshold versus roll angle b. Tracking (360m radiusat 88kph) Offtracking c. Handling Handlingdiagram (22,6) 1.Steering gain at 80kph andcritical speed versus 2. Criticalspeed at lateralacceleration (231 o3s Constant Deceleration Frictionutilization and Brakingeff iciency Stopping decelerationversus at 0.49 pressure Low-speedCornering (123m radius,9Oo Maximumofftraeking (ln-TownCorner) ggrner) TransientTurning Steeringwheel angle Lateralacceleration (Ramp-Step$teer) (Z00o,zsto 28o) responsetimes (50% steeringto 90%of steadystatel ObstacleEvasion Transferfunction: Maximumrearward (Rearward lateral acceleration of amplification (steering Amplification) last unit to that of the frequency{ O.5Hz firstunit Respondingto Transferfunction: Maximumclosed-loop External Disturbances steeringcontrol to steeringgain equivalentdistu rba nce input Brakingin a Turn (2sbraking pulse Open-loop:maximum . while following a 360m changes in yaw rate turn at Sokph) andsideslip Closed-loop:deviation from a referenceyaw rate indcpendentof the instantarleou$position or path of the performanccsigrrature has a discontinuityin slopeat the vehicle.(.onstant acceleration maneuvers arc inherently point (0,369)where the scmitrailer's inside wheels lift off of thistypc. Transient maneuvers may havccither open- the ground.The maxirlum lalue of lateralacceleration, or closed-loopversions, In thiscase, the ramp-stepand the rollover thrcshold,occurs at 0.39gwhen the tractor's low-speedcornering maneuversare treatedin an open- inside rear wheelslift. Above 0.08radof roll angle,the loop lashion.C)bstacle evasion and brakingin a turn are slopeof the curve (lateralaccclcration versus roll angle) investigatedusing both open-and closedrloopanall'ses, becomesnegative, indicating points of unstableequilib- and the rcsponseto external disturbancesis studied rium, through closed-lctopcalculations. The roll performancesignatures of vehicleswith full Open-looprcsults serve to definethe accident-avoidance trailersinclude additional accelcration versus roll angle capabiliticsoi the vehicles.In this study, a driver curvcsI'or each full trailer.Nonlinear spring characte ristics represcntation(24)is usedto steerthc vchiclesto attempt to follow prcsclectedpaths in simulated closcd-loop situations.These closed-loopanalyses aid in under- .40 standing the influencesof open-loopvehicle properties .9re on thc predicted performanccof the driverlvehicle z syritcm. Ezc E U J o .t6 PerformanceSignfltures and Measures { [-"d.o SteadyTurning F

Roll 08 t? .20 RQLL ANGLE (rodions) Equilibrium valucs of roll angle are a function of Iateral acceleration,as illustrated in Figure l. This Figure 1, Roll porformEnceBlgnaturo

865 Expertment al Sd, ty Ve hicle s and free play when leaf springs go into tension cause achieving this type of performanceat highway speedson more complicated-looking characteristicsthan those highwaycurves, Ilorvever, small deviations I'rom thc path shownin F igureI . Nevertheless,thc rrtllovcr tltrcshold is of the front axle havecaused trailer wheclsto strikecurbs readily identilied as thc maximum attainablelevel of and tlther roadside obstaclesand thereby precipitated lateral accclcration before rollover of any unit of the rollovers or control dil'ficultics, Recognition ol' this vehicle. dangcr has prompted the rccommcndationof a tracking 'Ihc first row of Table 3 providcsfirst-order estimates tesr(2I). of the rollover thresholdsof fully laden versionsof For a givenlcngth of vehicle,low-speed mane uvcrability various types ol' articulated commercial vehiclescom- is enhancedby adding articulationpoints. The addition monly employedin the United States.(Tablc 4 prcscnts of articulation points will greatly reduce low-speed prototypicalvalues of fundamentalpararrlctcrs dcscri bing ofltracking. However, this improvcment in low-speed the basicvehicles.) ln additiontrt thc ratio o{'ccnterof ofTtrackingcontributes directly to thc amountof outboard grirvity (c.g.) height to track wiclth,these estimates are ol'ftrackingat high speed. influencedby thoseconditions that allow the c.g. of the A specificturn hasbeen selected as being representative sprung mass to translate Iaterally-specilically,low of a high-speed exit rrrmp, The simulated maneuver is suspensionroll rates, free play, and low roll center performedat a vel()cityof 88km/ h (55mph)on a llat turn heights(9).Accidcnt data havebeen used to show that with a radiusof 360rn( I,200ft).The outboardofftracking small changesin rollovcr thrcsholdcan have a large attainedby the cnd ofthe last trailer hasbecn sslected as influcnceon the numbcr of I'ollovcraccidents for heavy the performanccmcasure. vchicleshaving values ol rollovcl thresholdsin the Figurc 2 is a pirramctersensitivity diagram showing the vicirrityof thosegiven in Table3(10). inl'luencesof (a) the corneringstil'l'ncsses of the tires,and (b) the wheelbaseof the third trailer on thc high-speed offtracking of a typical triple combination employing Tracking 'l'he 8.lm (27ft) trailers. abscissavalues of +l and *l Ideally, the trailing units in an articulated vehicle representdcviations from the baselittevalues of wheclbase would be expectedttl firllow exactlythe path rtl'thcI'ront and corneringstiffness. These deviations ar(: $qualtotVz axle ol'thc towing unit. Practicalvehicles cornc close to of their baselinevalues. At low speed,thc offtrackingon a

Table 3. $ummary of performancemoasures for basicvehicles

Tractor-SemiTruck-Full Trailer Double Triple 3-S2 3-2 2-51-2 2-51-2-2 1. Rollover Threshold(g's) 0.385 0.410 0.404 0.404

2. High-speed Offtracking(m) O.22 0.411 0.411 0 582

3. CriticalSpeed at 0.3g(kph) Nonexistent Nonexistent 130 130

4. G-Levelat NeutralSteer. Axle lifts 0.388 0.328 0.328 50mph f irst

5. BrakingEfficiency atO49 (Loaded) 0.88 O.77 0.78 O.BO {Empty) O.59 O.5O 0.55 0.61

6. MaximumTransient Offtracking(m) 4.25 2.88 3.48 4.74

7, Lateral Acceleration ResponseTime (sec) 0.80 O.7g 0.98 O.98

8. MaximumRearward Amplification 1.OB 2.O3 2.O7 2.96 Section4, Technical.Sessrons

Table 4. Fundamsntal parametere for tha basic vehiclet

Tra ctor- Truck-Fu|| Semitrailer Trailer Doubles Tractor or Truck 3-S2 3-2 2-51-2 weight (Newtons,N) 69,OOO 187.000 59,OOO c.g.height (meters, m) 0.88 162 0.95 front axle to c.9.. m 1.54 4.48 1.08 c.g. to rear susPensioncenter 2.11 1.44 2."8 c.g. to hitch (5th wheel) 1.75 4.14 2.3 total cornering stiffness,N/deg 21,300 20,200 12,900 brake gain per front brake, Nm/Pa 779. 775. 779. brake gain per rear brake, Nm/KPa 1169, 1169. 1169,

Semitrailer weight, N 287.O00 141,000 c.g.height, m 1.99 1.99 5th wheel to c.9.,m 5.78 3.52 c.g. to rear suspensioncenter, m 519 2.88 c.g.to rear hitch,m 6.10 3.79 total cornering stiffness.N deg 16,700 8,500 brake gain per brake, Nm,/KPa 1169, 1169.

FullTrailer weight. N 169,000 156,000 c.g height, m 1.87 1.92 f ront axle to c.g. 282 3.20 c.g.to rear axle.m 2.82 3.20 c.g.to rear hitch 3.74 4.1I total cornering stif{ness,N.deg 17.500 16,900 brake gain per brake, Nm,/KPa 1169. 1163.

Note: The triple i2Sl-2-2) is the same as the double except that it has another full trailer 'I-he 360m (1,200ft) radius turn would be 0.19m (0'62ft) +l value of deviation rcprcsentsthe cornering toward the insideof thc turn, As speedis increased,the stiffnesstypical of radialtires, thc 0 valuecorresponds to -l offtracking decreasesto zero and then increasestoward bias-plytires, and representslug-type tires. Although the outside.The basic triple is predictedto track more lug tircs are not usually usedon trailers,the parameter than .57nt ( L9ft) outboardin it maneuverrequiring 0. I 79 sensitivitydiagram shows thc advcrseeffect of low at 88km/h(55mph). corncringstiflhess. The triple tracksoutboard of the doubleby an amount equalto thecontribution of a full trailcrsince the double arernade up of idcnticalunits. The triple has by oFFTRACKTNG(ft) [rfr ; o.3o5 m] andtriple (OUTBOARO} far the lirrgestofftracking irmong the basicvehicles (sce aal thc secondrow of Table-1).

2.5 Handling "Q------In thiscontext (i.e., steady turning), handling refers to a ol the towing unit to steering inputs' r.5 the responsc Handling diagrams(22)(see Figure 3a) have been constfuctedat tlOkm,h (50mph)to obtainperformance 10 'l'hc ---l signatures. handlingcliagram contains a handling . ftO Trdilei whselbose curvethat displayssteady-tr.rrnirtg properties as a function O.S | lateral yaw rate,forward velocity,and a a Co.ne.in9 stilfness-3rd.Tror! of accclcration, I referenccfront-u,heel anglc (in this case,steering-wheel -{o -o5 0 05 anglc divided by stcering-gearrirtio). or the first DEVIATIONFROM BASE VALUE Vehicles with tandcmaxles on the tractor semitrerilcrdo not havea uniquchandling curve applicahle axles Figure 2. High-speedofftracking, paramstsr censitivity at all Fpccds(6).However. vchicles without tandem diagram do have specialhandling diagramsanalogous to tho'ie

867 Experimental Safety Vehicle s

acceleration.The fourth row indicatesthe lateralaccelera- tion levels at which the vchiclcsbecome neutral steer whiletraveling at 80km/h (50mph). ;4 o F TRUCK For vehicleswith full trailcrs,the handlingresults are d FULI. E TRATLER-*l UA /*OOUBLE similar to thosethat would havebeen obtained if the full l- 'Ihat trailershad been removed. is, conventionaldollies 4'? nearly dccouplc thc full trailer I'rornthe unit towing it a hecauscthc latcral force at the pintle hitch is very small F.l{ cornparcdto the tire forcesacting on the towingunit( l4). For cxarnplc.thc handlingresults for the double o and -,08 -,o4 O 04 ,OE triple are pr.acticallyidentical to thoseobtained if only I L r/U) - Delto(/odionr) the tractor-semitrailcrportion of thescvehicles werc to be analyzed.(The handling resultsfor thc doubleand triple Figure3a. Handtingdiagram are also identical to each other sincc these vehiclss ernploythe sametractor-scrnitrailer as their towirrgLrnit.) used in the study of passenger cars. Figure 3a contains At turning levelsa bove 0. I 59,Iatcr.al load trrrnsl'crhas handling curveli for a truck-full trailer and an important inf lucnce 'Ihe 'Ihe a double on truck tire characteristics. combination. handling curv$ for the double is curvature of tire corncring stiffness with respect to applicableto all spceds sincethis doublehas single_axle vertical load becomcsespecially important Ibr the drive suspensions.The truck in thc tr.uck-lulltr.ailer combina- axlcs ol'thc lcad rrnit sincca largeportion of the lateral tion has tandem axles at thc rear of the truck, l-or the loird transfer takes place at these axles on typically truck-full trailer, thc handling curve only applics at suspendedheavy vehiclesin the lJnited States.(iiven a 80km/h (50mph)becausc, due to thc tandemaxles. the bias in roll stiffnessdistrihution, the lcvelof oversreerar ellectivewheclbasc changes with velocity(6).1.he wheel_ high g lcvclsdcpcnds to a largccxtent on thc curvatureof baseused in Figure is 3a the rjistancefrom the I'rontaxle the tire charactcristics.The resultspresented here are lbr to the centerof the rear suspensionof the towinc unit vehicleswith typicalbias-ply truck tires, having a moderate (i.e.,the trrrck ). amount of curvature in their characteristics.However, In the handling diagram, an overstcercondition is suddentransitions to largeoversteer rnay take placefor indicatcd positive by a slopeof the hanrllingcurve. For tires with considerablccurvature in the relationship vehiclesthat becomc oversteerat lateral acceleration betweencornering stiffness and vcrtical load. levelsbelow their rollover thresholds, critical speeds have hccncornputcd. For thescvehicles, a stahilityboundary ConstantDeceleration Braking can bc plottcd in a spacedcfined by criticirl speedirnd laterirlirccelerirtion (see Figure 3h). t'hisstability bounclary The performance signature is a specialtype ol'performance signature that provides selectedfor constant de- celerirtionbraking is a family of curves(onc for an indicationof theconditions under which the driver has eachaxle) showing the to ccrntrolan unstablcvehicle. I'riction, required to avoid wheel lock, displayedas a function of treadleprc$sure (see For thebaselinc vchicles, the results indicate that all of Figure4). Also superimposedon thisplot isa graph them remainstable at speedsup to BBkm/tr (55mph)and of deceleration lateralaccclcrertion Ievels bclow 0.39. Thc third row of Table3 liststhc criticalspeeds obtained at 0.3eof lateral r.o

F z s.6 E r D E e,3 z ts z o o F J 50 !J .e ! E 40 o E 30 B 5101520 tr 20 BRAKE LINF PRESSURE(o/" of moximum) 1O o Figure 4. Friction utilization and deceleration, empty o,t.?.3.4,5 tractor-ssrnitrailer (interaxle LATERALACCELERATTON (o's) load transfer for the semitrailer'standem equal to Z0 porcent of Figure the braking torque divided by the tandsm 3b. Griticafepeed versus scceferation spread

868 l Section4' Technical Sessions

in g's versustreadle prssriure.Braking efficiencyis the of the trailer hasa maximum inboardofftracking of 2.9m ratio of decelerationdivided by the highest required (9.trft).which occurs whcn the reitr axle has turned frictioncoefficient (i.e., the results ftlr axle4 in Figure4)' through59'. The braking cl'ficiencyat 0.4g has bccrnused to provide The rnaxitnum olftracking of the rcar of the last unit the performance llteasureslisted in row 5 of Table 3. hasbecn used to quantify low-speedturning performance These results indicate that cmpty heavy vehiclcshave of the prototypicalvehicles (see Table 3, row 6). braking efficienciesthat are lcssthan 0.6. shown in Figure4, the braketorque ln the exarnple Ramp Step Steer actingon the tandemsuspension of thc tractordocs not transfer'Hence, the curveslabeled 2 'l'his caurieinteraxle load mancuveris used to establishthc quickness of the in Figure4. Curves 4 and5 do not coincide and 3 coincide Iatcral acceleration responseof thefirst unit in a cotnbrna- in this cxanrple,a signil'icantanlount of Ioad is b$cause, tion vehiclc,Response tinres are measurcdbetween the from axle 4 to axle 5 during hraking. The transferred timc whena rapidstccring input reachcs50 percentol its ol this interaxle load transfer is to reduce the el'lect firral valut and thc time when thc lateral accelcratton I'iciencyat 0.49from 0.59tor a vehiclewithout braking ef responsereaches 90 pcrcentol'its steady-statevalue. The load transf'erto 0'43 lbr a vehicle with a interaxle magnitudeof this resporlsctime dependson vehicle whosetandem suspension has a largealll()unt semitrailer loading, speed,and the amplitudc of the stecringinput' load transl'er(for Americansuspenstons)' -fable of interaxle The resultsgiven in 3,row 7.arc lor low-arnplitude steering-wheelinputs (2tl') applicdto l'ullyladcn vehicles Transient Maneuvers travelingat 80kmlh (50rnph)on high-ftictionsurfaces' The rcsponsctimes of thc basicvehiclcs range from 0.79 to 0.9tts. The lateral accelcrationrespon$c time is believedto Tractrix relateto the tnannerin which driverscorrect for external to one 'fhe disturbances.A computationaltnethod, sirnilar tractrix pertainsto the path of the axlesof a term used in vehicle testing(25),has been developed by while it is turninga corncrat low speed'To semitrailcr MacAdam(26) for asscssingclosed-loop response to offtracking at low speed.articulated evaluatetransicnt externaldisturbances. Rcsults from thesecomputations are treated as a train of semitrailersin heavy vehicles for the basicvehicles indicate that drivcrs,representcd by path of eachhitch is thegeneral curve f'ollowed which the a delay time of 0.25sand a previewtirnc of l'5s, will scmitrailer. by the attached increasethe magnitudeof the intluenccsol external The trajectories(tractrices) ofthe variousaxle sets ofa 'Ihc disturbances,occurring at approximatcly3rad's' by a trailer arc shown in F igure5' centerof the truck-full factor of approximately2. Theseresults irre sensitive to is assumedto follow a 90oturn with a ladius steeringaxlc driver-controlcharacteristics (delay time and preview of 12.3m(4lti), The rearaxleso{ the truck aretreated asa 'Ihe tirne). Shorterdelay times andl or longcrpreview times dolly axledocs not olltracktar frorl the singleaxle. will reducethe gain ol the closed-loopresponsc. path of the truck'srear axle (see Figure 5). l'hercar axle

ObstacleEvasion THE TRACTRIXOF THE VEHICLEIS: The obstacle-evasionmancuver is based on traffic conflictsin whichanother vehicrle stops or suddenlypulls out in the path of a heavytrr'rck. The truck driver is assumedto attempt to avoid a collisionby sucldenly swervinginto another lane. Vehicleperformirnce in this type of situationdepends on the pcriodof the rnaneuver and the forward velocityof thevchicle' Quick maneuvers, in whichthe ma.1or steering activity occtlls within 2s' have bcen found to excitcamplified responses at tht: lastunits of cornbinirtiotrvehicles with tull trailers(15). te.3m -CENTER These amplified rcsponses,relcrred to as rearward anrplification,havc been studictl in both tirne and 'l lrequencydomains. hc {rcquencydomain approitch has beenlorrnd to beeffective because ( l) theworst frcquency, thc one causingtnaximum amplification, can hc reirdily (2) ol the amplification Figuro 5. Tractricosfor a truck-full trailer observctl,and the magnitude Exp enm entalsqfery Ve hi cl es

determinedby linear methodshas proven to be a good transferfunction lrom that pintlehitch to thec.g. ofthe indicator of the magnitudcof amplil'icationpreaictcd by last fr"rlltrailer(5). I he rearwar<1anrplification of the norrlincar analyscs(l -5). tripleexcecds that of trrcdo*bre by a murtipricativeractor Rearward amplification not only has tracking or that dcpcrrdsprimarily on whcre the last pintlc hitcrhis swept-pathimplications, it also indicatcssituations in located,the length ofthe lasttrailer, and thc ratio ol.the which full trailcrs with high c.g. loadsare likely to roll weight of the last trailer divided by the sum ol. the over.Since the rollover threshold is expressed in terrnsof cornr,r'i'gstitfnesses of all ol thc tiresinstalled lateralacceleration, on the last the ratio of the lateralaccele r.ation of trailer(-5). the last unit divided by the lateralacceleration of the first Sensitivit.yanalyses havc shown that rearwardamplifi_ unit of a combinationvehicle has becn used to quantily cation may be rcducedsignificantly hy (a) rcclucingspced rearward arnplification. In the I'rcqr.rencydomain, this (thc resulrsgiven here ar.ear ttOkm/h (S0rnph)),(b) ratiois displayed as the amplitude of thetransl'cr.function increasingthe whcclbasesof full trailers,(c) between rcducingthe themotion of thec.g. of thetowing unit and the distance from thc centerol'gravity of a unit to the nintle motion ol thc c.g. ol'thc last unit (seeFigurc 6). The hitch installedat the rear of that unit, arrd(cl; incrc:asing maximum value ol' this transf'cr function has bcen the corneringstiffnesses of the tires. selcctcdas a performancemea$ut.e for this rnaneuvcr. 'ftr produce a closed-loopversion of the obstacle_ evasion maneuvcr,a path is selccrtccJto represetltthe choice made by the tJrivcrin an attemptto avoiclthe obstacle. 2.7 l)river-controlledpath tbllowing isthen uscdin pr.climinary the simulations(24). resultsfor a maneuver in z ?.4 whic-hthe driver attcntptsto suricienlytranslate the basicdouble o ?.t by a lateraldistance of l.2m (4ll) while E travclingat 80km/h (50mph)show a rearwardamplifica_ g t.8 tion of approximatelyl.-5 if the driver hasa 2s preview g and is allowed an aclditionalls (a totirl of 4s) for (L cornpleting t.5 thc l.2m (4f't)clisplacernent. Howcver, the E last { t.2 unit will not experience nrore than 0.lg of lateral o accelerationin this casewhere the drivercan usea lons preview E .9 timc. lf the previewis ^,;hortencdto l.t)san

The g .l.able Braking in a Turn results,given in row of 3, indicatethat tractor-semitrailershave srnall amounts of reirrward Combinedbraking and stecringmaneuvers are dilTicult amplification conparcd to vchicleswith full trailers.T.o to control on a poof, wet road.When brakingis applicd first approximation, rearwarrJarnplification is a cumula_ while turning, the dr.iverrnay lose directionalcontrol tive property consistingof the product of transfer mornentarilyor wheelson inclividualaxles may lock I'unctionsbetwccn (a) unit c.g.'sand hitch points, up, and( b) leadingtojackknifes or trailerswincs. hitch pointsand unit c.g.'sfrom thc front to the rearof Iirom an analyticalpoint thevehiclc(27,5). of view]hrakingin a turn is Hcnce,vehicles with morcunlts tcnd to difficult to treat becarrseit inl,oll,csail the dy,nirmic havchigher amplifications, 'fhe modes of vehicle motion. Fol cxample, tires are requireclto the basictriple is obtainedby addinga producc both longitudinal ancl lateral force, On evcn full trailerto thc basicdouble. The rearwardamplification moderately slippcrysurlaces, clernancl of the triple is approximately I.orhigh decelera_ equal to the rearwarcl tio' may resultin a lac-kof'sicie lirrce. Trrc critical levels of amplilicatiotrol thc doublc rnultipliedby (a) the transl.er perlormance, wherc loss of control miry functionfrorn the c.g, of thefirst occur, are i'ulltrailer to thepintle significantlyaltcred hitch between by rnanyvehicle characteristics. T,he thc first and secondfull trailers,and (b) the interaction betweenIongitudinal a'd rateraltire f.rces is

870 Section4. Technical,Sessrozs clearly critical, but data describing the influencesof deciding the tradeoffs betweenconflicting performance longitudinalslip on lateralforcc and slip angleare not requlrcrnents. gcnerallyavailable. The two rnainareas in which tradeoffsare reqrriredare Not only are the basicresults diflicult to predict,but (I) ctlmprorrlis$sbetween high- and low-speedtracking, suitable performance signatures and pcrlormance and (2) the choicebctween longitudinal and lateralforce measuresarc difficult to select.ln open-looptcsting. the capabilityin contbinedbraking and steeringnrancuvers. disturbancesin yaw rate and sideslipshortl_v- alter With regard to tracking,thc addition of articulations brakinghavc bcen usecl to quantifythe rnagnitudeol'the within a given overalI length can increaseoverall directionalcontrol ploblcmprescnted to thedriver(28,29). maneuverability,but it also incrcascshigh-speed off- Closed-loopresults have been predictedfor vehicles trackingand rearwardamplification. In conrbincdbraking equippedwith antilockbrakes(30). ln that situation,the and turning, truck brakcs in the United Statcshirve simulated drivcr does not need to modulatc brake traditionally been ablc to override the lateral lbrce prsssure.Howcvcr, inlornration is not availablcto useirt potentialof all tirescxcept those on the front axle.The predictinghow drivcrs will nrodulatebrake pressure driver is cxpectedto stesrout of ditficultiesalthough it when thc vehicledoes not haveirn antilock system, may bedil'l'icult or nearlyimpossible to avoid.iackkniling C'urrently,our plansare to pcr{'or-rnopen-loop calcu- on slipperysurlaces. lationslirr emptyand lully ladenvehic-les tuf ningat 0.I lg Adjustableor adaptivecomponents are being developed at 80km/h (S0nrph)on poor, wet roads(skid rrumber at to resolvesituations that currentlyrequirc compromises 65km/h is28). (Scc (30) l'or a discussionof tireploperties and tradeoffs.Fur example,antilock braking systems applicableto trrrningand brakingon a poor,wet road.) havc beenand arc being perfected.Also. new typesof 'l'he maximumdeviations in yaw rate,sideslip angle, and dolliesarc bcingconsidcrcd. ldcally, these dollics would articulationangles (where appropriate) will bc usedto changctheir characteristicsdepending on vchiclespeed euantify the influcnccs ol the disturbancescaused by and the type of mancuverthe driver wantsto perforrn.If braking.The brakeswill be appliedsuddcnly and fully. properlydeveloped, these autornatic svstems will aid the At thecnd of 2sfrorl the iniliationof braking,the brake drivcr in avoidingcontrol difficrrltics while. al ttresame pressure will be releascrl.The maximutrr clcviations time.not limitingthc driver's abilities and responsibilities occurring(a) when the brak$sarc appliedand (b) after for safevchicle operation. the brakes are releasedwill be used as performance measurcs. Ciivcn the above braking disturbance,closed-loop References sirnulationswill also be run to study driver;'rehicle "An systcm performanceduring braking in a turn. lf the l. NHTSA ContractDTNH-22-83-C-07187, resultsof thcsecalculatio ns ( hoth open-and closed-loop) evaluationol the I'actorsinflucncing heavy truck are significant,they will be inclrrrlerlin the previously dynamicperlormance," Contract Technical Manager: mentionedvehicle dynamics handbook. W. Leasurc. "Road 2. Mailtikarjunarao,C.. tankdesign: its influcnce on thc risk and economicaspecrts of transporting Conclusion gasolinein Michigan,"Ph.D. Thesis, The Univcrsity of Michigan,1982. "Roll The constraintsthat vehiclecharacteristics place on the 3. Mallikarjunarao,C.. R.f). Ervin.and L. Segel, obstacle-avoidancecapabilities of' the driver/vehicle rcsponseof articulatedmotor trucksduring steady' systen havc beenevaluatcd using performanct: measures turningmancuvers," AS M E WinterAnnual Mecting, derived from computationsbased on open-looptrlancu- Novcmbcr l9lJ2. 'l'ablc "Static vers (see 2). C'losed-loopcalculations are now 4. lJcrnard,J.E,, and M. Vanderploeg, and being used to exatninecontrol difficultiesthat may dynamic off'trackingof articulatedvehicles," SAE develtipin obstacle-avoidancesituations. Paper800 t 5l. 1980. '| "Tracking hcseresults provide information that should neces- 5, Fancher, P.S., et al., and stability of sarilybe considered by personsspecifying and assembling multi-unit truck combinations,"U niversity of articulatcdcornmercial vehicles. However, these results MichiganTransportation Research lnstitute, Report are not sutficientin themselvcsto providethe guidance No. UMTRI-84-25,July 1984. "The neededto assemblea satisfactorycombination vehic[$. 6. Fancher, P.S., static stability of articulated In particular,two furthersteps need to betaken. First, corrrmcrcialvehicles," V'ehit'leS.r'slern D.ynumics, a synthcsisproccdurc is neededto dcfinethe sequencc of Vol. 14.1985. "Effects choices(priorities) so the vehicle willsatisl'y its functional 7. Ervin, R.D., et al., of tire propertieson truck requircments-for example,low-speed maneuverability and bushandling," Final report,Contract No. IJOT- ' in small areas. Second, guidance is neededto aid in H5-4-00943, Highway Saiety ResearchInstitute,

871 Experimental Safety Vehicles

Universityof Michigan, Report No. UM-HSRI_76- report, Highway SafetyResearch Institute. Universitv ll, December1976. of Michigan, .,The Repor.tNo. U M-tISRt-I'F-71_1,Junl 8. Ervin, R.D., et al., yaw stability of tractor_ I,1973. semitrailersduring cornering," Final report, Contract "Contribution 19. Mischke, etal", to thedevelopment of No. DO'I-HS-7-O1602,Highway Sat'ctyResearch a cencept of driving mechanicsfor commercial Institute,Unive rsity of Michigan, ReportNo. UM- vehiclcs," I)aimler Bcnz AG, SAIi paper g30643, HSRI-79-21,Junc I979. I 983. 9. Winkler, C.8., P.S. Fancher,and C,C. MacAdam, "Parametric 20. Rompe,K., and Ii. Heissing,..Methodsof objective analysisof heavy duty truck dynamic descriptionof the handling characteristicsof heavy stability," Final report, Contract No. I)TNH-22-tt0_ commelcial -fransponatron vchicles,"XXth I. ISITA Congress,May C-07344, University of Mic-higan l9ft4. ResearchInstitute, Rcport Ntl. UMTRl_93_13, March 21. Nordstrom,O., anclS. Nordmark,.,'I'estprocedures I983. for ..Influence the evaluation of the latcral dynamicsof com_ 10, Ervin, R.D., ct al., of size and weight mercialvehicle combination s,,' Au to mo b il_I ntlusrrie. variableson thc stability and control propertiesof Edition 2, June 197t3. heavy trucks," Final report, Contract No. "sirnplilied FH_l l_ 22. Pacejka, H.8., analysisof sready_state 95'77, University of Michigan Transportation turning behaviourof motor vehicles,,' Vehit:le Slt.srem ResearchInstitute, Report No. UMTRI_g3-10. Mav l).r,no*,tt, 2pp. l6l-183, pp. lg5-204,1973. 198-3. "A "Mechanics 23. MacAdam, C.C., computer-birscdstudy of the I I. Segel,L., et al., of heavy-dutytrucks and yaw/roll stabilityol'heavy trucks characterizerj bv truck combinations,"University of Michigan Engi_ high centersof gravity,"SAF. Transactions, Vol. gi, neeringSummer Conference, .Iune l3_17, lgg3. "A SAE No.821260.I983. 12. Morrison, W.R.B., swept path modcl "Application which 24. MacAdam,C.C,, of an oprimalpreview includestyrc mechanics,"proceedings 6th Conference control lor simulation ol' closecl_lclopautornobile oI'theAustralian Road RcscarchBoard, Vol. 6, part driving," IEEE Transportatiotr on S..t,stems,Man, l, Canberra.1972. ('.t.t,herneric.r, "Vehicle and Vol. SMC-ll, No. 6, pp. 393_399, 13. Sayers, M.W., off-trackins models." 1981. Symposiumon GeometricDesign for Lrirge Trucks, 25. McRuer,D.T,, et aI.,,*Measurementof driver/vehicle TransportationRcsearch Board, L)envcr, C olorado, multiloop rc$ponseproperties with a single dis_ August 1985. 'l'ransportarittn turbance input." I EEI:' on .5l,srt:nrs, I4. Ervin, R.D., et al.,.,Ad hoc stuclyof certain safety_ Man, and C.yhernetits,Vol.5, No,5, 1g75. related aspt:ctsof double-bottom tankers," Final ..Frequency 26. MacAdam, C.C., domain methodsfor report to Michigan Statc Oflice of llighway Safcty analyzing the closed-loopdirectional stahility and Planning,Repofi No. UM-HSRI_78-lg, Mav 7. maneuverabilityof drivcr/vehiclcsystems," t978. lnter_ national Clonl'erenceon Moclern Vehicle Design 15. Mallikarjunarao, p. ,.Analysis C., and Fancher, of Analysis,London, 1983. the directional responsecharacteristics of double "The 27, Fancher,P.S., transientclirectional response of tankcrs,"SAE Paper781064, I)ecember. lg7g. full trailers," SAE paper821259, lgB2. 16. MacAdam, C.C,,et al.,',A computerizedmodcl for 28. Ullelmanrr,F., "Stecringbehaviourol'motorvehicles simulating the braking and steeringdynamics of under braking," 2nd Course on Atlvanced Vehicle trucks, tractor-semitrailers,doubles, and triples System Dynamics, InternationalClenter for Trans- combinations-users'manual,"Final ReDortMVMA poltation Studie$, Amalfi, ltaly, May Proj. 2g-.Iune l, I197, Highway, Safety Res*a.ch Institute, I984. Universityof Michigan,Reporr No. UM_HSRI_g0_ "Vehicle 29, Rompe, K., handlingcharacteristics during 58,Septembel l, 1980. braking proceerjings ,.Truck in a turn," Eighth Internarional 17. Gillespie, T.D., et al,, and tractor_trailer Technical (lonf'ercnce on L,xperimental Safety dynamic responsesimulation _T3DRS," Final Vehicles,Wolfsburg, October 19g0, report, Conrracr No. FH-l l-9330, Highway Sal.cty "lntegrating 30, Fancher,P.S., antilockbraking sysrems ResearchInstitute, Universityof Michigan, Report with the directional control propcrtiesof heavy No. UM-ltSRI-79-38,March t979. trucks," Intcrnational Clonfercnceon Antilock 18. Bernard,.I.E., tt.B. Winkler,and p.S. Fancher,..A Braking Sy$temsfor Road Vehicles,Institutc of computer-Lrasedmethrld for preclicting the i rectional

872 Section 4. Technical.Sesslozs

TestProcedures and EvaluationCriteria for the HandlingCharacteristics of Heavy CommercialVehicles

Klaus Rompe and Table I is a surveyof the measurcmcntresults available Bernd Heiping in the literature on the driving bchavior ol'heavy Institute for Traffic Safety,ttiV Rtreinland commercialvehicles throughout thc pastdecade. From e.V., Cologne,Federal Republic of (iermany this.it canbe gathclcd there arc trasically five eligible tcst procedu res: L Steady state turning to determine the under- Ahstract steer/ov'ersteer behavior as a I'unctionof lateral accelerationor drivingspccd, yeari In the past, quitc a number of relevant test 2. Brakingduring steadystate turning to determine procedures,including appropriate criteria ol description, the yaw stabiliryand steerability. havebeen conceived to detcribeobjectively the handling 3. Lane changeto determinethe stceringeffort and characteristicsof passengercars and passcngcrcirr-trailcr the efi'cct ol' a lane change as an excitation combinations.lJecause of thevarious design principles of function lirr yaw angleoscillations. comrnerc:ialveh.icles and the ever-incrcasingadvanccs of 4. Stepstccr ing input to determinethe promptncss vehiclecombinations insuring optimum utilizationof of vchiclcresponse. space,i.e., single trucks or buses,truck-trailer combina- 5. Frequencyresponse m€asureffient to determine tions, scmitrailcr combinations,articulated buses, plat- theextent and prornptnessofvehicle response as form roadtrains, and short coupling truck corlbinations, a functionoi'thc steeringangle input. handlingcharacteristics the ofthescvchicltls are definitcly Figure I shows the required measuring variables more distinct from each oth$r. A descriptionof the illustratedby theexample of a truck-trailercombination. handlingcharactcristics as compared with existingdesigns Thereris evidencethat the standardvariables referring to will bc of great irnportanceto classil'ication tl'rc of ncw the tawing vehiclesuch as liteeringangle. driving speed, vehiclccombinations. This papergives a surveyof the lateraland longitudinalacceleraticln, and yaw velocity measuringproccdures applied far so and the findingsa$ are neededand soare corresponding measuring variables publishedon the handlingcharacteristics o{'hcavy com- 'l'his referringto further element$ol'the combinationand the vehicles. approach mcrcial is cornparedwith relativcyaw anglesat the diffcrentjoints or couplings. measurementstaken by theauthors lbr a l6t tluckr.a J8t truck-trailercombination, and a spccialtype 38t semi- trailcrcombination. Against this background. the trans- vr r @'llorho v.lft'tt ferability of the test procedures,which havepreviously &l,Arror'v+ YdF^nitr ASI: a.ul+ rilhr r!h rdbl. beenapplied to passcngcrcars only, and the required Loq,hrd'^ol / lqrrdr restrictionsunder their application to heavycommercial vehiclesis illustratedand evaluatedon the basisof the mcasurementresults obtained. Any measuringvariables and criteria of descriptionthat are of significanceto this particularclass of vehiclesare detailed.

Current Status of Test Procedures

'1 The registration regulations as applicable to com- Figure . Commerclal vehicle maasuring variables mercialvehicles are specifying requiremcnts to beaccom- modated by mainly two irreasof the handlingcharac- teristicscomplex, viz., straight line braking and mobility SteadyState Turning in turning.Since these procedurcs have been applied for quite a long time, they will not be treatedIurther in this Steadystate turning is to provide data on the steering paper.The examplesdetailed in thesections to lbllow are tendency,i.e., on the driving courseas a function of ratherrclated to the lateraldynamics and the combined stecringangle and lateral acceleration. Thc conditionsIor lateral and longitudinal dynamicsof hcavy commercial implernerrtationrclating to passengercars are specified in vehicles. an ISO standard(22). Figure 2 illustrates the characteristiccurves of a I ln chargc of tht Germln Frderal Minister of Transporl steering angle increase over the lateral accelererticln

873 Expeimental S"fety Vehicles

Table 1. Measursments of driving behavior of heavy commercial vehicler

Test Procedure Vehicle,Mass Author

DoubleDecker Bus 13t Rompe 1971 t1l Truck-TrailerComb. Nordstrdm 1e77 t21 Bus 11t, 16t Benedek et al. 1978 t3I Steady State Truck 16t-22t Falkner et al. 1978 t41 Special-TypeTank Winkler et ar, 1978 t51 TruckComb. SemitrailerComb. 26t,38t Emery 1s80 t61 Turning Truck 8t-1 9r Krisper et al. l98l l7l SemitrailerComb. 1Ot,36t Burg 1981 t8l Truck-TrailerComb, 8r-38r Gauf erar. 1982 tgl Truck-TrailerComb. 8r-381 Hei/Jing etal. 1982 tl0l Special-TypeSemi- trailerComb. 40t Heiliing r 982 t11I Truck-TrailerComb. 8t, 12t Alberti 1983 tl 2l SemitrailerComb. 38t Helber etal. 1984 118l

SemitrailerComb. 1ft,25t ltami et al. 1974 tl3l Brakingduring SemitrailerComb. Fancher 1975 tl4l SteadyState SemitrailerComb. lot, 36t Burg 1e81 t81 Truck-TrailerComb, 8t-381 Heiling 1e82 t10l Turning Special-TypeSemi- trailerComb. 4Ot Hey'Jing 1982 tl 1l ArticulatedBus 16t-271 Bruns et al. 1984 tl gl

SemitrailerComb. 38t Gau/ etal. 1973 tl5l Truck-TrailerComb. N0rdstrdm 1e77 tzl Lane Special-TypeTank Winkler etal. 1978 t5I TruckComb. Truck 16t-221 Falkner et af. 1978 t41 Change Truck 8t-191 Pilz etal. 1981 tl6I Truck 8t-38t Gaufi et al. 1982 tg] Special-TypeSemi- trailer 4Or Herling 1S82 t11l ArticulatedBus 16t-27t Bruns etal. 1984 t19l

Bus,Truck Weir et af, 1974 t2o] StepSteering Bus Bisimis 1978 l17l Bus 11t, 16t Benedek et al. 1978 t31 Truck 8t-1 9t Pilz et al. 1981 t16l Input Truck-TrailerComb. 12t Alberti 1983 tl 2l SemitrailerComb. 38t Helber etal. 1984 t181 SemitrailerComb. 38t Gaufi et af, 1573 tl5I Frequency Bus Bisimis 1S78 I17l Bus I 1t, 16t Benedek et al. 1978 t3l Response SemitrailerComb, 38t Helber etal. 1S84 tl8l Measurement Truck-TrailerComb. 8t-38t Hamann 1984 expressedas the differencebetween thc steeringangle d, steeringcharacteristicri, The handlingcharacteristics are minus the steeringangle nccdedto drive on a circular rather governedby both the steeringcharacteristics and path at thc smallest Iateral accelerationdn.o.*. This the yaw anglesacting at the singlejoints. variable, also known as understeeringindex, permits Figure3 illustratesthe steering angle and sideslip angle turning maneuverson different but constantradii to be of the towing vehiclcof a loadcd l6 to 22t truck. Also illustratedtogether. Whilc theunderstcering tendcncy is illustratedare the yirwanglcs at the couplingpoint A*, distinct for all the loadedsingle vehicles illustrated in the and at the turn tableA*r. Whilethe sidc slip angle of the upper part of the Iigurc, it wasi'ou nd to be comparatively towing vehicleincreascs with the latcralacceleration, the smallfor individualtrucks. Ilesidcs, F igure2 showsthat a two yaw anglesand hencc the trailer's position to the trailerwill not alwaysbring a bout a significantchange in towing vehicleremain almost constant, A deviationof l Section4, Technical.9esstoas

200 ,d tdtel O tio { .E oo { Bus 16t l3l r { Truck16 t [71 t00 E - Trucl 16t I 101 r l0 6 g F a 8zo k d -r0u16

Righi lat{rcI A.celtrulim lm/tz I ?

r\ { r0 - si* sriptuqrr p d ---- Tutn Tdbto Angt. AIY? "" to+cI ro -^--- RllotivrYow Angtr ${1 F

b 6

Figure2. Steering angleincrease - 6 H - 6H,Ack as a function of lateral acceleration a" during $t6ady state turning (all vehicles with maxi- mum permissibleweight) Figure3. Steeringangle, slide slip angle, yaw angle' 'and ring mount angle of a truck-trailer steady state turning the trailer from the circularpath or a lateraldisplacement combination l38tl during (truck with trailerl, R= 1G5m. maximum wasobserved.'lhis phenorrlenon isstated to ot'thetrailer permissibleweight, dry roadsurfacel(101 bc a criterion lor the evaluationof steadystats turning, e.c,,(2). Anotherimportant criterion isthe maximum physically lm/s2. When comparingthcsc values with the valuesof obtainable lateral accelcrationduring turning. It is modcrnpassenger cals. onc will lind a Iateralacceleration naturallyhighly dcpcndenton the respectiveccntcr-of- of 6.I throughE.2m/ s?, which will decreaseonly slightly gravityheight. Table 2 isa listingof maximumvalues, as with incrcasingload(27). measurcdby the variousauthors, for the vehicletypes whcn drir'ingon a dry roadsurlace. As loading in driving testsis genctirllyof a low cetrter- BrakingDuring Steady State Turning of-gravity hcight,fcrr more practicalpurposes, the actual valuesare assurred to beslightly lower. One will seethat The test procedure ol braking during steady state thc r,aluesobtaincd lilr singlt-.vehicles and combinatiorrs turning was designedto yield itrfortnatiotrabout the agreementantj that the maximum extcntto whicha vehicle'ssteering behavior is influcnced are in reasonablc 'l'he physically obtainablc latcral accclcratiot'twill in an by thc simultaneousacting of brakingforces. criteria avcragedecrease under loading conditionsby about for cvaluationare measuringvariables that describethe

Table 2. Maximum lateralacceleratiorr during turning on a dry road turfsce 17,8,9,1O, 20)

Maximum PhysicallyObtainable Lateral Acceleration

VehicleType unloaded loaded Bus 4.7m/s2 Truck 16-?2r 4.4-4.5m/s2 3.6-4.2mls2 Truck-trailerComb. 3Bt 4.1-4.5m/s2 2.9-3.4m/s2 SemitrailerComb. 38t 5.5m,/s2 3.9*4.2m,zsz

E7s E xpe rim ental Safety Yehic Ie

capacityto keepthe course,yaw stabitity, and steerability application over the rcspectivedeceleration. with For minor distinctdecelerations. lhe dralt standarclprovided variations in the startingconditions to be equalzed,the for passcngercar brakingduring turning(231 liasto be yaw vclocityand lirteralacceleration adaptcd for are relatedto the heavy commcrcial vehicles,especially in original values,and thc vnr.iationol theside slip anglc as terms ol' starting conditions, becausethc physically comparcd with the initial state is plotted. A refercnce obtainablelateral accelerations are lower durirrgiurni,r! curvc is used for evaluation purposes.The underlying and decelerationtakes molc time tti setin. principleis that a vehiclewill continueto Tho time functions tr.avelexactlt plotted in Figure4 relatingto yaw along the initial r:adiuseven after brakc applicationani vclocity W, lateral accelerationar, side slip angle p, that decelerati.nand sideslip angle wirr rernain c.nsta't brakingpressure p, and deceleration a_were dctcrmined durirrgthe brakingrnaneuver. for a l6t rruck with permissibletotal weight(10).With a Figure 5 showsthe evaluationfunction of the lateral meandcccleration, hardly any dcviationswere obscrved accelerirtionlbr an urrloacledl6t singlctruck, a loaded in comparisonwith a pas$engercar. Unlike this. thc l6t and a 22t truck, and a specialtype 40t semitrailcr vibration of lateralacceleration was found to bc distinct combinationwith antilocksysrem (AtlSX with glcat dccelerations, l0,l l). Experi_ This can be attributed to ence has slrown that an initial lateralacceleration of pron.u'ccd pitchingmotions resulti'g fr.om the i'itiation 'l'his 2m/ s2 and an evaluation instant ol. 2s altcr brake of braking I'orccs. behavior of' the truck testcd applicationat an adequatclyhigh initialdriving velocity persistedwhen it was coupledto a trailer. 'l'he are I'it for the purp()sc, lower hall of the figure The evaluationfunctions arc established by deriving illustratesalso the yaw angles reference at thecoupling p,rint t*, values from the time functions, which were .l-he and the turn table A*, ol'the combinationtruck. measuredin single tclits at the rcspectivedeceleration incrcasinglocking tcnclency,of'the truck with rncrcasins levels. Such referencevalues are synchronousvalues dccclerationwill rcsultin growingyaw angles. obtained from the single With ttri tests,e.g., I or 2s after brake towing vehicle near.ingthe limit ol. steerability,the decrcasingyaw anglcs polnt to the almost straicht posrtion of the unit. In the ABS vehiclea controld*ulce will precludc thislimit I'rornbeing r.cachecl. Thrs will lead to a minor incrcascof yaw anglesbel rvccn the elancnts of the combination when coming unclerthe inl.luenceof

1,2 -,-,- TruEt qtq Troctor 5 dld t,0 / Tmiler l-- r ---- Truck + Tmiter 0,f ! Ro=105m; drsr?m/st E lt\ -E if 0 E b 5 F; p 2.5

Ttuck+ Troiler; - RrlotivrYowArytc Atlt ---- furn TabtrAngte Al.yl

Figure5, Comparisonreference values for brakingduring ste.SdV$tate turning Figure4, Time functions of characteristics for a singletruck, I truck- measuring trailer combination variablesfor braking (AAt),anU a specialtype duringsteady state turning semitrailer 1av'o?m/s2.R = 108m, combination (4Ot; 1sV."_2m/s2, truck, drive road R = 105m, surrace,maximum permissible maximum pe.missibleweight) weight)(10) (1O,11l

876 Section4. Technical.fessiozs

again. A short steeringangle impulse as greatdecelerations( I I ). Comparahle trends ofthe evalua- straight ahe.ad passctlgcrcar-trailct- comhinations will not tion function wcre establishcdby (8) also. Although appliedfor generatean adcquateoscillation encrgy in comparativetcsts hirve rarely be en prrblishcdso far' it can sulficc to vehicles( I l). be assutnedthat Figurc5 is represcntingthe likcly range cotnmercial Table 3 summetrizesthe maxinrumvalues obtained for of evaluationcritcria as valid lirr the vehiclecategory in combinations.both loirdcdirnd question. diflerent truck-trailer whcndriving on two roadsurlaces(9)' The lane In view of the different respon$ehehavior of towing unloadcd. was intendedto be Stttttver a distanceof vehiclesand trailers,it will be reasonableto incorporate displacerlcnt With no load or uniformly distrihuted loacl,the in the analysisnot only the evaluationfunctions but also 40m. moverncntsof thc trailerwcrc estaLllishcdto be thevariation with timeof themeasuring variablcs 2s after lateral wet, antiskid asphaltpavcmcnt at a driving initiationol- braki ng. l.5m on velocity ol about SOktnlh and on a lessskidding blue basalt surface (moistened)at about T0knrlh Whcn Lane Change changingthe laneat the highcstpossible vclocity trailer oscillatiorr,paths 01 -lm aud ovet'ctttl be ohscrvccltor dual purposeirt This tcst proccdureis applicd to servea both surlacetypes. I he vibrationpaths established for ol heavycom- the evaluationof handlingcharacteristics the unloirdcdtruck-trailer combinatiotrs were on an mercial vehicles' averageslightly shorter as courparedwith the loaded combinations.With thetrailer rrnlal'orahll' loirded' c'g'' conditions,in some Evaluationof TrcnslentSteerlng Behavior onli' in the back third, the driving cases,turned ottt to be tnuch Inolc critical. : To climinatc the driver inlluenceon the measured The driving coursechosen, e'g'' by (4,l6)' is the dual it will bc a meaning{'ulapproach to evaluatcthe ISO lanechange(24), which is to be understoodas a lane results. as a lunction of the actualvehiclc cxcitation as displaccmentol'3.5m ovcr a distanccol'30m' With this' results by theyaw tnovcnlentor thc lateralaccclera- thscvaluationwill covcrthe stecringactivit-v cspecially, reprcricnted in thecoupling i.e.,the amount of rcquiredstccring tnovclnents to ht: tion Points(21)' Figurc 6 showst heposition of theelements of a special made by the driver to first keepto thc laneand thento 40t semitrailcrcombination after traving passed the stabilizethe vehicle. type singlelane displacenent o{'-1ll over a distanceof 40rnon a wet. hardly skirjrlingsurl'ace at a ls interval(ll)' This Behavior of Evaluation of the Damping clcarly proves the validity ol' the proccdurefor the Combination Elements applicationof newvehicle combinations also'

In this test,which is basedon a cout'scsinilar to the change,c.g.. in thc l'orm of a single(9'll)or ISO lane SteeringBehavior dual(2)lane changc, the lancchange will mrrinlys$rve to Transient excitethc cotnbirtation'soscillation' l'hc aint of thc test of thc steeringactivity during lane procedureis to detertrtinc thc darnpingof theyaw angles The evaluation hasproven to be a suitabletool to dctcrminethe an.i tl't. oscillationpaths at the cnd ol the trailer' change characteristicsduring rapid steeringtnotlons, The mcasuredvalues will thcreforebc recordcdonly harrclling steeringbehavior, afterthe lanchas been changed and thevehiclc is driven i.e..transient

for driving velocity.vn Yaw angle in Table 3, Maximum values reached during single lane chtngs ur, and {or the tateraldisplacement at the the couplingpoii* ,1..,-"-. and atihe tlurntabte *2*", trailerend s.ur(9)

Truck-trailer vmax f lru* Q?^^* s.ax conrtlinations (degree) (m) 32t and 38t (km,zh) (degree)

unloaded 85-75 0'6-10 /=0'8 loaded 75-85 25-35 1.6-2.8

unloaded 70-75 28-45 24-35 1.0-2I p=o'3 loaded 72-80 15-35 1.7-3.8

877 Experimentdl Safety Vehicles

delay periodsincreasing with loading,as compareclwith passenger cars.lior a l(lt bus with pernrissibleloait. the decclclation is 0.05 to 0.I(Js as cornpirr.cdwith an unloadedvch icle(-l). Figure 7 illustratesthe basicallydifferent tendency in vehiclercsponse between a hus(17)and a modernpas- sengcr car(27)excrnplif icd by theyaw velocity. While the passenger carsreach a maxinrumvalue about 0.1 to 0.5s after stecringinput (50 pcrcentrating), the motronal variablcsreferring to the buschangc over into the steacJv statevaluc aperiodicnlly.In adclition.the figureshows the distinctlydecelerated response bchavior of thc bus cornpared with the passcngercar.. Mcasurenrents taken 1'orscrnitrailer cornbinations(l2,lg) indicatea similar .'',r.{fi*i behaviolwith no reaching of themaximum yaw vclocity +|lc. Trfi,hr/ lroitrr or wrthoutcxcessivc 8o|olt. l.tl overswing. v,' 72,5 Detailcd km/h comparisonson a litcraturebasis cannot be made bccausethcr.c is no information availableon series of mcasurements with different driving velocitiesand lateral ac-cclcrations.I his will surely be clue to the Figure 6. Positions cornparativclylargc after an extreme change of lane for spaccneeded to con

Step SteeringInput Yr=lmkm/h ?ar.orr, =Lm/gt Bur:o,+, =5mzs? The step steering input as applied to commercial vehicles is comparableto that appliedto passcngercars. A draft standardon rhis subjecthas bcenprcparecl(25). .f Thc driving velociriesrangc from SOto AOtm/h with transient obtainablelateral accelerations of 2.5to 5m/ st. Thc steering o wheel'srotational speetl rnay rcach from 300 to 500'/s. I Bccauseof the different,and in parr not s exirctly stated,definitions of thc clelayperiods betwecn steeringinput and yaw vclocity or laferal accelcration bcing usedas an evaluationcriterion, and becauseofthe ditterent Tihe t Isl starting conditions,rhc resultsobtainecl by diffcrent authorscan hardly bccornparcd. As a basicfact, the essentially Figure 7, Comparisonof vehicle higher incrtia mornents alone of the responsein the Btep steering input test commercialvehiclcs will naturallycause essentially for I bus(171and 14 longer pa$s6ngercars(ZSl

Table 4. Test conditions some and resurtsfor the test procedurestep steeringinput Vehicle u u"'oo T aso,ni,soy. lkm/h) 1m/sz) (s) Bus,Truck (17,ZOl BO5 *l Semitrailer comb.(12) 68-72 3.5-3.8 0.4-0 32t unloaded 5

Semitrailer towing comb.(10) vehicle 3 0.2-0.3 38t toaded 54-59 trailer o,7-1.0 Section4. Technical,fesslozs

FrequencyResponse Characteristic semitrailercombinations, from the frequcncyresponse cha riict r;r'istics. Measurcrncrrtsof amplitudefrcque ncy charactcristics The determinationof the frequencyrcsponse charac- of the yaw velocityol a busalso show a rapiddecline in teristic of yaw vclocity, lateral acceleration,and yaw yaw rcsponsewithottt any distinctresonance point( l7). angle with periodicsteering input as describedin the To insurean all-inclusivccvaluation, thc phaseangle ISO/ DIS(26) pcrmitsa mor$ cxtensiveevaluation ol the characteristic,too, describing the promptness of a vchicle transicnt stecring behavior. The amplitude frequency responschas to betaken into account' Hardly anything is characteristicsol' this variablc rclated to the stecring known about suchmeasurclllents' 1o idcntilythe phase input are illustrated in F igure8 for a loaded38t contarner anglecharactclistic of thc yaw velocity,()lle catl usc the semitrailer combination at a driving velocity ol equivalentresponsc tinre ofthe frcquencyat a -45ophase 50kmt h(l5). The rapiddecrease of themcasuring variables angle.According to (21),the result will beabout 0.2s for with increasingsteering flcqucncy is indccd striking. an unloadedtruck at v = 80km' h' atrdithout 0'3s for an Given a stecringlrequency o{' 0.5H2, the obtainable 'f unloacledtluck-trailer combination. hevirlue ohtained latcralaccelcration has dropped to about 50 percentof for passengcrcars is I'angingfrorn 0.1 to 0'2s(2it). thevalue produced by thevery same steering input undcr transientsteeri ng conditions. Summaryand Conclusion

Wherranalyzing the pertinentliterature availablc on 5 Ea mcasurementstaken on the handlingchirracteristics 0f fe will casily find that H\ heavy cornrrtercialvchicles, one r.' for truck-trailer,and semitrailer E resultsare on hand buscs, combinatiorrsthat wereobtaincd trotrl a good many test 3 plocedures.Since the authors working on thissublect use always t.^ 7 dil'ierent startirlgconditions, the findingscannL-)t E* be compared. I+ ' 'I-hc d tcst proceduresapplied to determinethe handling 0 characteristicsol pirssengercars are basicallyapplicirble to commsrcialvehicles and combillittionsas well, ln F i:, doing so, one should hear in ntind thereis a needfor !e adaptingcither the startingconditions or the criteriatll' T descriptionaccord inglY. With rcgardtrt rclev;tnttest proccdures such a$ sttlady stateturning, b rak ing d uringtu rn ing, and lane changc, as wellas transient stce ring behavior,it is possible'itr stlme to indicatemeasuring rangEs or at leasttcndcncies Figure L Frequencyrgsponse charactsristics of a fully cases, loaded 38t container-carrying semitrailer for the behavior of heavycotnmercial vehiclcs tl-rat wilt combinationat 50km/hl15l provide a sound capability,e.g,, in conrparingnew vehiclccombinations. Under comparable conditions, passengercars are likely to reachthis value otrly with lrequenciesabove 'l'he lHz-. largeyaw inertiainhcrcnt in the commercial References vehiclcsf inris expressiotritr this phenorncnon.LJtrlike Kippgrenzevon Doppeldeck- this, the yaw angle betweenthe towillg vchicleand the l. Rompe, K., Die l, VDI-Verlag' trailer decreasesdistinctly slower with the stccring Omnibussen.t)KF-FIeti 214.l'97 "Test procedurc{'or the evaluation frequency but does not show ir pronoullccd resonance 2. Norclstrom,Ole, vehicle point. Other nleasuremclltstaken do' howevet',show of the lateral dynamics of .corttntercial TUV Rheinland,1977' sucha resonancepoint in therange of 0.3H2for a truck- combinations,"Kolloquium trailercombination(18) and 0.3 through0.(tHz lor an s. r68-193. Geller,and F' Rohinek, articulatedhus( l9). The amplitudc lrequencl'charac- 3. Ilenedek,A., I. Geller,J. "Ein von teristicofthe yaw anglecan be considered an indexofthe Beitrag zur Frage dcr Fahrstabilitat Rticksicht auf dic clampingproperlies of thc truck-trailercombination. Autobussen mit bcsondcrer oscillationbehavior of a Gunrrlireilen."FlSITA, I97u.S. t477-892' Comparahlefindings on the "Lenkkralte Feitzelmaycr. und combinationas dcrived from the lanechange tcst can be 4. Falkncr.W., and K. FISI lA. 1978.S. 245-255. derived cquirlly for combinationswith onlyone joint, i.e., Fahrzcugltandling."

879 Ex perimental Safety Vehicles

5. Winkler, C.8,, R.L. Nisorrger,and R.D. Ervin. k gen "Tcsting raftfahrzeu bei zeitlichve16nderlichen euerkri{f- the Michigandouhle-bottom tankcr," SAE ten. DKF-Helt Nr',232, 1973, VDI-Verlag. Paper "Lcnkverhalten 7810fr6. 16. Pilz, H., and H. Stumpf, von Lkw- trrnery, "Limited 6. L.H,, yaw stability of trucks and Reifenim l-aborund aufder Strape," FISITA, 1980, tractors,"Proceedings Eighth International Technical t.3.4. "Fahrverhaltensvergleich Conferenc-eon ExperimentalSafety Vchicles, 1980. 17. tsisimis, E., zwischen 1 Krisper, C., P. Rcichwegcr, and P. Piihringer, Omnibus Personenkral'twagen," "Einflup und FISITA, Ig7g. von Fahrzeugparameternauf die Fahr- s. 173-179. dynamikvon l-astkrafrwagcn,"F ISITA, 1980,1.2.3. 18. Helbcr, R. u.a., Sicherheitstankfirhrzeugfiir brenn_ Burg, H,, "LJntersuchung des Fahr.-uncl Br.crnsver- barcund explrrsibleFltissigkeiten, Phase I, Daimlcr_ haltcnsbei eincm Sattelzug," DEKRA Symposrurn, Bcnzim Aultragedes BMFT. 1984. 1981. 19. Ilruns, H., G. Matyssek, and G. Stangl, Fahr- 9. Gaup, F., H.-D. Hamann, and H.-Chr. I'flug, dynarnischeUntersuchungen an cinemSchubgelenk_ Fahrvcrhalterrvon Lastziigenund hierbeiinsbeson- bus,A'fZ, 1984,S. 5-51-554. "Analysis dere von Anh.lngcrn.FA1 SchrilicnreiheNr, 30, 20. Weir. L).H.u.a.. oftruckand bushandling," r982. Final report,t)OT-HS-tt0l*153, 1974, STI. "Versuche 10.Heiping, 8., and J. Ehlich, Fahrverhalren von 21. Harnann,H.-D., zumGrenzlhhrverhalten schwerenNutzfahrzeugen unclZtigen bcirn Bremsen von schwerenLastzrigcn," I)iss. Universitht Han_ in derKurvc, DKF-Heft Nr.281, 1983, VDI_Verlag, nover,l9[i4. I l. Heiping, 8., "Untcrsuchung "Road einesspeziellcn Sattel- 22, ISO 4138-1982, vehicles-steadystare circular zuges,"Bcricht Nr. 954782003TUV Rheinland(not testplocedure" publishcd),1982. 23. ISO/ I)tS 7975,"Road "Mcssungen vehicles-braking in a turn* 12. Alhcrti, V., der TU Braunschweig,"(not opcn loop testprocedure." publishcd),1983. 24. ISO I R 3888,"Road vchicles-double "Directional lanechange," r3. Itami, S., and M. Oda, stability ol' t975. tractor and scmi-trailer "Road combinationin braking," 25. ISO/DIS 740I, vchicles-transicntresponse Bulletin o.fJSA E No. 7, 1976. testprocedures (stcp/ramp input)," 1982. 14.Fanchcr,P.S., "Prediction '[C] "Road of brakingand directional 26. ISO 22 SC 9. vehicles.-lateraltransient responscsof commercialvchicles," HSRI. [Jniversity rcsponsetest plocedurcs," t)oc,, 1983, ol Michigan.1975, "Variation 27. Rompe, K., and E,.Donges, rangcsfor the r5.Caup, F., and H. Isermann,Wankbewegungen, handlirrgcharacteristics of today's passengercars," Radlastschwankungenund Kippgrenzcnvon Sattel- SAE Papertt4ll87, 1984.

Tractor SemitrailerUnit for the Future

Pierre Soret r We show here specificelemcnts related to safety RenaultVehicules lndustriels in all its erspectsbut undcrconstraints of other heavycomponcnts o1' thc generalspecifications. It mustbe seenas the global approach and response of Abstract the makcls.

For the truck maker, safetyis a major componentof Introduction-Safety and Truck the general specifications. However important this conrponentmay be,it is only one itemamong others; 'l'he For the truck maker, safetyis but an clementof the r goods transporrvehicle for 2000induces a general truck specilications,however important this break in -fhe all fieldsof performance. elemcnt may be. clesigner'schoices come under a r Particularlyfor safcty,we havedeepened major global compromise bctweena set of otlen conl'licting locking areasas the rollover phcnomena. obligations.The cost of the product cornparedto the r We haveclaborated, with otherrelated industrics, market price is a major limit to the evolution of in a completeprogram namedV.l.R.A.G.E.S., performancc.Furthermore, different specific constra ints an experimental tractor-liemitrailer.unit, pro- (safety, environment, energy, etc.) often induced side viding substantialimprovements in all fields. evolution proce$sesof vehiclesthat, to instantlv meeta Section tl. Technicul Jessrloas requirement(either legal or regular),have hampered the V.I.R.A. G.E.S.- GeneralSpecifications developnrcntol'other featuresof the transportvehicle. For instance,thc takingofan under-runstructur$ or a Cicneralspecifications ol this vehicleaim substantially retardcris surelyan efficicntlactor ol'tral'l'icsafetv. but it highcr than the prsscntindustrial practice in the fieldsof is an cxtra cost and cxtra wcight that appreciahlyand encrgy,environrncnt, coml'ort, and satety,but of reason- directlyaft'ects the economy ol transportation.I n Europe, ahleacccss, at leirstf rom an cxperimcntalpoint ol view, this step-b1'-stcpevolution of the transportvehicle has b1'rneans oi'new technologies. beenthc main featureof thc past 20 years. As lor safcty.thc aims were worked out with thehclp of The margin answenithcn brought leacjnowaday$ to a the NationalOl'tice tbr Road Safety(()NSER). technicaland economical compromise ditficult to improve, especiallywhen we want to usethe new technelogiesfor Safety the rrrostsatisfactory ccotrtrrrtical ccinditions. Fr"rrther- Primary more, thc vehicleis not thc rcsponsibilityof only one maker. Cu$tom has separatedtwo typesof industry; Ride, I{andling, and Rollover r The powcr vehicle r The towed vchicle.trailer. or semitrailer The following prone factors were defined and This dislribution of activiticshas subslantialconse- numericallyaimed: quenccson safetysincc in this iield.rlore than in others, r Driveabilityin evasivcmotion pcrlormanccol'the convoy has to be considcred the r Road handlingin curves rather tharrthat ol the $eparatevehicles. r Rollovcr rcsistarrce Also. we rnust noticc that weight and dirncnsion To sum up, the main line is an improvementot the regulationsdo not takr into accountthe capital clcments maxirnumtransversc accelcrati,rrn within thr bthaviorof of the transversalstability of theunits. lt is truethat, on the vehicleis satisfyingIrom 3.5ms'2to 5ms-?. this point, different influencesoppose each othcr and compromiscsare needed:for instancc,motor vehicle/ railervehiclc n'rnss ratio, and the ability to turn within Braking the rcgulatedswcpt circle. To sum up. the analyticanrl marginapproach that has The following accident-pronefactors have been selectedr prevailedin the evolutionof safetyof goodstranspor! r Stability of ttretrajectory during braking vehicleshas reached its Iimits.lt hasto hc replaced by a r Brakingpower mere synthcticapproac-h that (l)associatestruck and r Action dclay trailer rnakers,and (2) intcgratesthe demandfor safcty r Nonlockingol wheels -l into otherstrong dcmands related to thegeneral evolution r ightnessof the circuits of roadtranriport-. energy, environmcnt, driving and use conditions,and productirity. Visibility and Lights Renault V6hiculeslndustriels undertook to answer this type of demand,along with relatcdindustries under r Quantified improvcmcnt of forward. side.and the aegisof ths authorities( Ministblc dc l'tJrbanisme,du bacrkvisibility field Logerncntet des1'ransports and Agence}rranqaise pour r Modulationol lightsaccording to luminosity Ia Maitlise de I'Energie)according to a programcalled r l-owrring splashirnd spray V.l.R.A.G.E.S.(Experimental and RcscarchTransport Notc:The detection of proximityol'the vehicle running Vehiclelmproving Energyand SafetyPerformanccs). ahcador bchind was not includedin this study.It has We presentthe outlineof this prograrn,especially as it been consideredas relevantto auxiliary techniques, to salety. brrt still kccping in mind we have relates which are relativelyeasy to integrate,and havinglittle integrated the need for a global irpproachto satisfya inllucnccon the architecturcof the vehicle. compromisein appreciableevolutiorr in all directions. 'l'he project is backed hy generalspecitications of thc high-rangeroad vehicle,3ll/40 and 44t, a tractor- SecondarySafety semitrailerunit. lt doesnot systematicallycomply with existinglcgulations, and the choicesmade may allow Three accrdent-pronefactors were concerned; l,alorizationand quotationol'certain trends in rcgulations . In priority, non-undet'-tunltingon the front for and standards. passengervehiclc. in caseof front-to-lront shock An experirnentalvehicle, thc firststep toward thc aims r Sideguard against two-wheelers and, il'possible, of the gcncralspecification. is undergoingtcsts.Another, parscngercar! aiming at a substantialbrcak in perlormancc,is in the I Rear undcr-ride deviceas an improvementof study phaseand plannedfol tcstingin late 1987. resulationsin force

881 Expertment al Sofrty Ve hi cIe s

Snfety in Use 3. Making a more stableexperimental convoy by modifying a standardtractor and dcsigninga Nonquantiliedlines werc defined for thedriver's safety vcrryto rsion-resista nt, three*axlesemitrailer wit h that relatedto wolk around the vehicle: axlc-by-axleadjustable rolling stiffness, r Accessto the cab 4. Test campaignon this unit for measuremenrsas . Rorlm for life aboard in stepl. r Coupling/uncoupling operations The conch.rsionshelpful to a designercan thus be r Loading/unloading opcrations resumed. Last. considerationsrelated to driving comfort but l'he sensitivityto rollover of articulatedconvoys is due with positiveretuln on saletyare included in theprogram, mainly to the bad coherenccof load transfersin rolling suchas controlautonatisms or drivingaids. rnetton. J'he rollover limit can be apprcciably improverl by RelatedAnalytic Works makinga stifferchassis and by a rollingstilTness according to thesuspended load per axle. It isthus possible to come 'l This project hasled to increasingknowledge of physical closcrto the theolcticalrollover limit. his lastdepends phenomenal'or- on simplegeometrical dinre nsions such as thc gauge and o Front-to-front shocksfor passengercar$ versus altitude of the cenrcr of gravity. To improve it, the heavyvehicles following will haveto beconsidcred: outlines that usefor r Rollover ol articulatedunits the bestas much of the gaugeas possiblc(regulations' The first irreunder devclopmentand will bc presented lirnit); developmcntof low, largetires; and suspension with the secondexperirncntal vehicle. The sccond has with trim correctionto lower as much as possiblethe beencompleted and the rcsults have heen communicated semitrailerfloor and the centerof gr.avity. to the 1984FISII-A Congressin Vienna.They conf'irm ln transient motion, roll and yaw are dynarnically the work of other researchcrsin thc United States, stable. llowever. it is useful, in order to takc the best Europe,and Australia. advantageof good geometryand cohcrentstiffnesses, to The program hasbeen carried out through four steps; adjust the other parameter$of thevehicle so thetransicrlt l. Test campaignon a standardtractor-semitrailcr rcsponseis correctlydampcd while keepinggood driving equippedfor measuringthc rollover limits in comfort. quasi-stationary conditiorrs, circru lar, eight shaped For the biggestlimit values() 4ms-2),the fifth wheel tra.jectories,and in transientconditiorrs (sharp backlashind uccs modil'ications in thc masstranslers that bend and evasivcmotion). it would be better to climinate. ?. Working out of mathematicalmodels of trans- It stillremains that, in limit conditions,theclrivcr does vcrse stability allowing the Iorecast oI' quasi- not perceivethe stateof the vehicleand socannot irttempt stationaryand dynamic bchaviors. corrcctive rnaneuvcrs.But the risk of this sitLration

Table 1. Primary safety

Splash Handling Roll-Over Braking and Visibility sPraY Field outrine Tractor 6x4 Semitrailer2Axles X X X 5-17.5'17.5=407 Singletire = Maxi Gauge X X Disc Brakeand A.B.S X Same Wheel 19"5 on all axles Low Large Tire X X High TorsionStiffness of chassis X RollingStiffness -nonlinear Xv -proportional loads High Cab LargeWindshield reachingcab floor X Six Sided Stream Lining includingtwin axles X Section 4. TechnicalSessions

Table 2. $econdarysafety

Agressivity PV,/IV Cab Floomand Driving Shock Access Comfort Aids Forwarded Front Axle X X Front Low Rigid Structure X PossibleFront Asborbing $hock X Area Six Sided Stream Lining X Sliding ' SingleDoor Right Hand Roof Safety Exit X X lnner Stairs FixedCubic Cab X C2.5m)3 Rotative Lateral Plastics Remove X ControlledWindow Automated Gear-Box X Air Suspensionfor Cab X

Note: For all tests. bicyclewheels were 600mm from edge of the platformand overtakingspeed was l Okm/h. decreasesif the convoy is built accordingto the rules prescntsrnuch itlrproved technological tlcvices, mainly in ahove-mentioned,and if, in consequence, lirrrit transvcrrje the field of thc structureatrd chassis conceptt having an accelerationis appreciablyincreased. important irnpacton sccotrdarysafety.

ExperimentnlVehicle*V.I'R. A.G.E.S. Conclusion Let us not forget this is a multicriteria experimental vehiclethat does rtot clllphasizcsafety hut irnprovesit, This globalapproach and the differentrelated funda- atong with othcr nceds ol' the gene ral and glohal mentalworks bring trcwktrowlcdgc to thc dcsignersof specifications. truck :rndtrailcr industnes. tt is the maker's an$wef, necessarilyrelated to 1-hcprogram V.l.R.A.G.E.S. allows evaluation of the compromises,not the safctyspccialist's. capabilitiesot' making other technicaland economical To simplify,we prcrjcntin thc shapcol'a matrix the compromises.It alsopcrtrtits a realbrcak in all ficldsof technical and technologicalchoices mirdc and thcir the gcncral specifications:fuel consunlption,safety, effectson safetycriteria selected(see'l'ablcs I and 2)' enl ironmcnt. driving and service,reliability, and Thesechoices concern thc first experimcntalvehicle. productivitv. It is a dil'ficult, netv. and erpansive 'l'hc secondtakes into accolltlt the same fuudaurttrtal experience. but it allowstht gootistransport ve l-ricle to be outlinechoices but covcrsthc ca$cof the4,lt cttnvoy and developcdin a satislactorymanner alter 2000.

Protecting Car Occupants,Pedestrians, and Cyclistsin AccidentsInvolving Heflvy Goods Vehiclesby Using Front Underrun Bumpersand Sideguards

B.S. Riley, design featuresdiscussed include height aboveground, strength,travel, and force-deflectioncharacteristics. A S. Penoyre,and 'l'ransport joint betweenthe and Road H.J. Bates programme ResearchLaboratory (TRRL) and TI Tube I'roducts l ransport and Road ResearchLaboratory, -fransport, Ltd. is dcsc:ribedfor the designand developmentof a Departmentof [JnitedKingdom front underrunburnpcr using thc plasticdcl'cllmation of rrrilclstccl tubes to absorbenefgy, and resultsofcar-to* 'l'hc Abstract truck lront impactare summarised. iinal ilcsignis able to protectseatbsltcd car occupantsfrom intrusion This paper starts with a reviewof accidentsituations from a frontal collisionat a closingspeed of 65km/ h, for requiring underrun bumpersand sideguards.Bumper a total bumper weight of approximately 60kg. lt is

883 Experinental Sdety Vehicles

recommended that any future legislation for front pcdestrianslikely to be savedby sidcguardsis about underrunguards requirc an energy_absorption 50 capability, (comparedwith 60 in 1976). and a possiblelegislertive test proceclure is outlined. 'l'his paper prescnrsfirst the rcsults of impact tests Testscarried out on sideguardsfitted to an ar.ticulated calried out on onetypc offront underrunguard fittecl to a goodsvehicle, using a simulatedpcdal cycle accidcnt, are rigid lorry, and then thc resultsI'rorn testing a sideguard described.lt waslbund that theinci

884 Sectlon4. TechnicalSesslozs significantsource ofcar occupantinjuries, and to reduce match the force at which the car front collapsesso that, at theseinjuries thc burnpershould be low enoughto hit the thc cnd ol' a severeimpact, both have crushed.The strong doorsill rather than the weak door. This will difficulty is that car l'rontal stillnessesdiffer greatly reduceintrusion and will alsoinsurc that the bulgeinto betweenlarge and smallcars, so a truck bumperttptimised the car will bc mainly below the occupantrather than for collisionswith small cars may bc too soft for large Ievel with his hips ol ribs. lf thc burnperface is :rbout ones.Since the proportion of small,ligtrt cars is increasing, l50mm deep.a maximrtmground clcarancc ol'approxi- and sinccthcse vehicles give lessprotection than bigger rnatcly250mm would be desirablelbr this sideimpact cars to their occupantsin a collisionat any particular case.The needto negotiateramps may demand a slightly speed,it is suggestedthat a smallcar (c.g.. 750kg unladen) higherfigurc, but {ortunatclythc burnpcris usually close shouldbe thc mostimportirnt design case chosen for the to thefront whcclsof thc truckand littlcincrcasc should underrunguard. However,it is essentialthat theguard be necessary. can also handlea collisionwith a heavycar without A rigid underrun guard of suitabledimensions would catastrophiciailurc. overcomethe structuralmisalignment problem and so Testswith a largc number of recentEuropean cars(3) would allow the car's strcngthand cncrgy-absrtrbing show that on averagea frontal l'orceof about 230kNis capability to be used to help protect its occupants. developedwhcn the crush reirches300mm, while local Current cars are designed to provide protection for pcak lorcesof about twiccthis size are measured briefly 'fhcsc occupant$wcaring seatbclts in a head-onl'rontal impact as the engine is deceleratcd. high lorces suggest into a rigidwall at up to 50km/h. lt istherefore probable that theburnper should be designcd to strokeat a forceof that a rigid truck underrun guard would prcvcntscrtous apprtrximatcly200kN. whir.-hwith a strokeof 3()()mm injuriesin truck-to-carcollisions up to thisclosing specd wouldgive an energyabsorption of 60k.1.This is equal to tor a heavytruck. and this would protectto a slightly thc kineticenergy of a lt-carmoving at nearly40km/h. higher speedIor a lighter truck. In reality,achieving this high constantforce will be Howcver, in car front to truck front collisions,the difllcult in a bumper that must be both light and cheap. vehiclesarc usualll'moving in oppositedirections so the Its desirabilityis questionirble.too. becauseit may not closingspeeds in thistype ol'accident are lrequently well strokcat all whenhit by a small,wcak c'ar t uPto about above50kmlh. To prot$ctcar occupant$at thesehigher 50kmth relativespeed. and damageand intrusionmay speeds,it is essentialthat thetruck bumpcris not a rigid then be bccorling crriticalfor the occupantsof sucha car. structure but dcsignedto yicld in a controlled way to AIso.lowcr speedimpacts occur tnore often than high- absorbpart of the ct'ashenergy. speedones, It is likell, therefore,that a force-dcflcction The energyabsorbed by the humperas it yieldsis, of characteristicthat startsat a comparativelylow level course,givcn by the area ol its force-deflectioncurve, (possiblyl00kN or rathcrless) and thenincreases as the and, for maximum absorption,as long a horizontal bumperstrokcs is prelerableto the constantforce one, strokingdistance as possible should bc uscd.It isunlikely despitcits lower energy-absorptioncapability. undercurrent legislation controlling vehicle length that operatorscould accepta bumper that initially projects beyondthe truck structure,while it mustnot movcback Design Details so far when hit that the cirrwindscreen pillars meet the truck chassis.Thus, thc total crushof boththc horrnetof A cheap and light method of dissipirtingenergy is to the car and the bumperof the truck mustnot begreater uscplastic deformation of stcelon thc inverttrbe principle. than the original length of the car's bonnet. Small After discussionwith severtrlpossible manutacturing bonnets(e.g., Mini, Metro)frequently extend only about partncrs,a joint programmcof wolk bctwcenTRRLand 90(lmm ahead of the baseof thc scrcctrpillars and can TI Tube I)roductsLtd. wasagrccdto usingthisapproach. crush approximately 500 to 600mm without giving The humper bar, a rectatrgularhollow steel section seriousintrusion into the passengcrcompat'turcnt. The l50mm X 75mm X 6mm wall thickness,was welded to maximum allowable stroke lbr the energy-absorbing two vcrtical drop arnrsabout 260mrnlong, which were truck bumper is, therefore,about 300 to 400mm. In pivotcdfrom brackctsbolted below the end of thetruck practice,of course,lack ol spaccbclow the truck front chassismtmber. Twrr itrvertubecartridges initially 450mm structuremay requirca shorterstroke than this for a long and able to be compressedhy 200mmjoined the frorrt underrun bumper. lowerends ol'the d rop armsto additionalbrackets bolted For a given allou,,ablestroke, the maximum energy- below the chassismcmber 100to 400mutfrom thc other absorptioncapabilitl' cr{ the bumperwould bc obtained brackcts(Figure l), by designingit to dcl'lectat a constanthorizontal force These invertubes consisted of two steel tubes of choserlto be the greatestthat can hc applicdto the car different diametcrs( 100and 80mm),the smaller of which without producing seriousintrusion Qr loo violent a was turned back on itself at out cnd and was then deccleration.In other words, thc buurperforce must peripherallywelded to the openend of the largcrtube. E x pe rim ent al Sa.fety Vehicle s

well below the figures measuredfnr car frontal streneths describedabovc hut comfortably higherthan the tOOtw requilcdby the {i&U Regulation468. Howcvcr, tests in which BL Marina cars (1,000kg) were impactedcentrally into thc bumper mounted on a $tationaryFord truck (5, I00kg)showed that thisbumper failcd to strokecomplctcly even in impactsseverc cnough to breakthe scatbclts of thedummy car occupants. In two testswith angled offsetand perpendicula, off .t Marina impactsat 50 rrnd64km/h, thc bumperdid not stroke fulll' but still provcdeffective in preventingunderrun and passengercompartment intrusion. A perpendicular central te$t with a l,550kg Vr.rlvocar at 56km/h also failed to stroke the bumpcr fully but bent the truck chassis seriouslyhehind the bunrperrear mounting brackets. It was thereforeagreecl that a rnajor rcductronin the strcngthsof the invertubes Figure 1, Invertube underrun guard was required,and this was obtained by using l6swg (l.63mm) thicknesstubes instead 'J-hese of l4swg (2.03mm). have a load when strokingof When a compressionload is applied, the smirllertube approximately47kN eachinstcad of I0?,kN and requirc progressivelytu.ns itseil insideout as it is forcccrinsicre a total horizontal burrrperfbrce of about 68kN thelarger tube ("like taking a sockol'f'"). After an rrnpactl to start $troking.T"he maximum energy_absorbing capability, the invertubcunits havc to be renlaced. of the invertubesis reclucedproportionally to about 20kJ. Theinvcrtube struts telescopc ut nearlya constantload It is no longer possibleto withstand the l00kN loads of Regularion over thcir 200mrn stroke, but the gcornetry of the 46IJbeforc stroking, but the geornetryol'thc underrun guard means thc horizontal force on the bumperis suchthat thisload is develooed when bumperapproximately dtluhlcs as the burnper bar.moves it strokcs about I75mm. Since the .egulario,, through requiresthat thc its strokc of 220rnnr.This is advanrascousas distanceof the bumper insidethe restof discusscdabove. the vehicle's strucrure must not exceed 400mm, this rcgulation passcd It is estirnatedthat an underrun guard to this design is hy the rnodifiedenergy_absorbing burnpcr, would retailIor.approxirnately f I50 plrrs VAT andfittiirg althoughrnost of its workingstroke is useduf during andthat the invertubc energy-absorbing cartridges woulJ the tcst proceclure, .l.he The costa bout f 3-5per pair to replace. totalwcicht ol.the weaker bumper was tested in another Marina head-on guard is about 60kg. central impact at 65km/h. It pcrformed well, stroking fLrllyand protectingthc dummy occupantsby leaving the passcnger Test and Developmentprogrflmme compartmentalmost undamaged (Figure2) w,hiledeveloping only moderateseatbelt loa

886 Section4. Technical Sessions

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Figure2. Damageto Marinacar f rom impactat 65km/h into front underrunbumper underrun guard,and it is to be hopedothcr designteams able impactors. Since some designsof bumper may be will be able to producecheapcr and lighter alternatives, verl' speed-scnsitivc(especialll, if they use hydraulic possibly by using hyrlraulic systems.H owever, thc energyabsorbers), an impact test rathcr than a quasi- Frogramme has clearly demonstratedit is fcasihleto staticloading test is essential,and thisshould be carried make sucha devicethat neednot be significantlyhcavier out at a fairly high specdreprcscntative of the maximum or more expcnsivethan an adequatelystrong rigid (that survivablccar-(ruck collisions, for cxanrple,50 or 60kmi'h. is, non-encrgy-absorbing)bumper. The theoreticalbe ne- The programmedesc:ribed abovc shows that thebumper fits in irnprovcdcar occupantprotection resulting from can readilvhe designed to absorb20kJ ol'energy, which thc useof an encrgy-absorbingdesign have been confirmed would requirean impactor massabout 200kgmoving at in practicalcar-to-truck impact tests. 50km7h or l40kg at 60km/h. The moving mas:;could eitherbe a trollcy or a pendulum,which would haveto fall throughnearly l0m to reach50kmrh. It is suggestcdthat to passthis testwould rcquire(a) A Possible Legislative Test Procedure for the maximumforce acting on thcinrpactor not to cxceed Energy-absorhingFront Underrun Guards 200kN (102gon a 200kgimpactor) at any time.(b) the maximum lorc-eacting on the inrpactornot to cxceed Widespreaduse of energy-absorbingunderrun guards l00kll during thc first l00mm of its movementafter for trucks, in conjunction with compulsory seatbelt corltirctwith thc hurnper,and (c) the maximum allowable wearing for car occupants,would produce significant horizontalDrovcnrent of theimpactor in thc directionof reductionsin deathsand iniurics.However. these benetlts impact not to cxceed400mm. The bumpcr rvouldalso will bc felt by the car occupants.while the cost of the halc to meetthe stre ngth and dimensionalrerquirements bumperswill fall on the HG V owners.It thereforeseerns of (&U Regulation468. unlikely that many truck operatorswill voluntarilyfit The width of the impactor face used in the energy- front underlun guards,and legislationwill be nccdcd. absorptiontests should representa narrow car engine This shouldbe draiied to requireu5s of cncrgv-absorbing bh,rckoi. say,200mnr. lts hcightshould be apprclxirnately bumpersrather than rigidones for thefronts of trucks,as 200mm and its grounclclearance also 200mm,so the explainedabtlve. l-he tcst specificationshould probably height of the top cdgc of the impactor would be 400mm use a rigid-facedimpactor to hit the bumpcr, thus aboveground level.The faceedges should be curvedto a avoiding the cost and rcpeatabilityproblems of deform- radiusof'about 5mm.

887 Expeimental Safety Vehicles

The testimpact would be carriedout both at thecentre nudgedby the sideof the vehicleor becomeunstable for of the burnper and ol'l'scrro oppositc rhc truck chassis somereason and topple toward the lorry, falling into membcrs;rlcw the cnergyabsorbcrs (or a newbumpcr) coukl path of the rearwhcrcls. be usedfor each impact. The truck would be buttcd up The accidentdata show that this isa relativelycommon against a rigid heavy block during the tcst impacts to causeol'death for cyclists,pedestrians are also run over preventits massaffecting thc rcsultand to insure that the by falling toward and under the sirleof HGV's. impact cncrgyis rrrostlyabsorbecl by the bumpersysrem. It is hopcd recommcndationsfor sideguarddesign The off'sctimpact test should insure that the torsional obtainetl I'rom the cycle test will also help protect strengthof thebumper bar and its.joints to thedrop arms pedestrians. is high enough for the drop arms to romain parallel during stroking, so the bumper'stotal energy_absorbing capahility will be utiliscdel'en in an offsetcollision. SideguardsUsed in the Tests

The Sideguards Basic Sideguard

The sideguardused as the startingpoint in the testsis An amendment to the United King

888 Jection 4. Technical ,Sessrorrs particular rrprightsand rails used.The sideguardin this Most of the testruns werecarried out with the vehicle form weighedapproximately 45k9. beingdriven past the bicycle at l0km/ h. Someruns were alsocarricd or.rt at l5 and 20kmih. The ExtendedSideguard Testswere donc with the dummy fallingagainst the sideguardat two positions(l and 2) atong thc basic from tests on the basic After analysing the results sideguardand at threepositions (0, l. and 2) alongthe in an to irnprovcits guard.changes were made attempt extendedguard, as shownin Figures3 and 4. This was to reducethe incidenceof running pclformance, both achievedby driving the vehicleover a rubbertube laid injury due to other over and to reducethe severityol across the tcst trirck. The tube was connectedto an causes. electricalair pressureswitch, which releasedthe magnetic view of the extendedguard is illustratedin An overall deviceholding the dumrnyand bicycle. with an actual ground Figure 4, where it is shown The speedol'the vehicle was controlled by usinga fifth Other ground clearancesof 400and clearanceof'300mm. wheel measuringdevice attached to the tractor unit. 450rnmwere also tested. condition because 'l'he Ten runs wcre carried out for each to be as close as guard was extend€drearward of thevariability with whichthe dummy could lall. lrrthis (Figure 5c) and forward possibleto the semitrailertyres way, a more meaningl'ulresult was obtainedin that a tractor wheels' as far as possibletoward the probability of ef'fectivenesscould he evaluated. weighed about The sideguard in its extendedform Each test run was recordedusing two video cameras increaseof -j5kgover the basicsideguard. It 80kg,an and recorders.One was so placed as to give a three- justify and cost would be difficult to this extra weight quartcr view from the front of the dummy and bicycle, guald proved to be tnuch more unless the extended and the other, a narrow anglefrom the front. effective.

,,. Test Results

TablesI and 2 list the configurationsof sideguard tested at thc various conditious ol overtaking specd, positionof impactalong the guard,and distanceof the bicyclewheels frorn thc semitrailerplatform. About l0 runswere carried out for eachte st condition. Informationsuch as whether the dummy cyclistwas run over or struck by the trailer tyreswari in part obtainedby observationat the tirneof thc test,but it wasconfirmcd, and rrlorcrje.tailed information obtained.by analysisof Figure 4, Extendodsideguaro showlng dummy impact the video recordings. Positions0, 1, and 2 A typical test run is illustratedin Figure 7' The first photographshows the dummy and bicyclc.iustafter the The SimulatedAccident magneticdevice had released the dummy (tirnet = '08s). The succeedingphotographs are at about 0.57sintervals The testconsisted of driving thearticulated lorry at low and showthe dummy cyclistlalling against the sideguard past a dutlrny mtluntedon a stationarybic.t"cle. speed anclthen to the ground.It is importantto notc that the and cyclewere released from their support Thc clummy dr.rrnmyis not attachedto thebicycle in any way.The only fall onto specificpoints along the and allowed to dit'ferenccsbetween the tcstcycle and irnordinary bicycle sideguard. are that the former hasa speciallyshapcd saddle to help generalarrangement is shown in Figure 6. The The keepthe dummy and bicyclcin a straightline and thcre wasatt RAE Mk5 atrdsat on the bicyclein the durnmy are fittingsthat allow the dummy handsto reston the a normal rider would. The dummy and bicycle sameway handlebarswithout slippingoff duringthe time between preventedfrom falling over by a cablcattached. via were releaseand impact with the sideguard'The clbow joints magneticrelease devicc, to a shoulderharness fixed to a of the dummy tr/crctightened just enoughto preventthe cablewas. in turn, attachedto a sntall thc dummy. The upper torso of the dumrnyslumping forward afterrelease enabledthe dummy and bicycleto be mobile cranethat from the supportingcable. All otherjoints wereloose, placedlcaning slightly toward the vehicleat an angleof about 5o and, for the majority of the tests,with the bottom ol'thebicycle wheels approximately 600mm from BasicSideguard Results the verticalplane passing through the edge of the trailer platform. A couple of testswere also carried out at a Beforestarting on the main tests,two runswere carried distanceof 1.000mm, out without the sideguardin place.In both theseruns, the

889 Experim ental Sqfe ty Ve h icles

(b)

(a)

ffi

(c)

Figure 5. Details of sideguards ' tuation 4. Technieal Sessions

dummy fell straight to the ground in the path of the scmitrailerwheels and was run over. The first six tcstswith the basicsideguard fitted, as listedin Table I, werecarricd out with thesideguard set in from the cdge of the trailcr platform by the maximum r allowabledistance, Four of the testswere at l0km/h and theother two at l5krn h, Two testswsrc carried oul with thc bicycle wheelsl,000mm from thc platlormedge and the restat 600mm. ,M that when the impacted at It was found dummy s { t.^r position l. at the lower speed,there was time for the w rtlt durlmy to slidedown theguard and, having reached the ii#,. bottom ofthc guard,there was suflicient ground clcarance for thc dummy to roll underthe sidcguard. It waslargcly a matterof chancewhether it rollc.llar enoughtoward ffiT thc trailer whcclsto be run over.Table 3 showsthat in 'l'cst l, thc durnmywas rull overin four of thc nineruns, giving about a 40 percentprobability of heingrun over. When the dummy inrpactedat position2, at cither specd,it had lcsstime to slidedown the guardand lall Figure 6. Dummy and bicycle before impact Table1. Basicsideguard test conditions

Sideguardconf iguaation Test condilions

H6drol guard Rearol guard Distance Whole gutrd {lar€dout lrom {laredout {rom Protective tub€ Upright6 Guard iarls Qvartaking of brcycle irrsetby half way Fornt, three quartar at luhtlion ol inset ltom tlugh wjth lmpdcl 6peed wheels trom haxirnum levelwrth edge point levelwrth load hooksaM gudrd rails edgaof posrlron (km/h) plattdrm edge allowed ol platform edge ot plaftorm l-sections olatform {mm) 1 x 1 10 600 ? x 2 10 600 3 x 1 l0 lQoo 4 x 2 10 1OOO 5 X ? 15 600 o X t 15 600 7 X t 15 600 I x 2 15 600 I X ? 10 600 10 2 15 600 l1 2 10 600 12 x t 10 600 13 x 2 10 600 14 I ro 600 tc ? 10 600

Nole: For tll lesrs,srdeguard gtound cleardnce55Omm when semrtrailerplatform lrorizontal. Actual groundcleardnci S95mntat front ot sideguard3nd 5 /t m/n at r€ar. Table 2. Extended sideguard tsst conditions

Sideguardconf iguration

Ground Distancein Protectivetube lmpact Tesl clearance of guard Uprights at junctions Position constant along railsfrom insetfrom of load hooks lengthof guard edge of platform guardrails and l-sections (mm) (mml 16 300 Flush X X I 1'l 300 Flush X I 1B 300 ta 1 19 300 75 0 20 300 Flush 0 2l 300 50 o 22 300 25 0 23 400 75 o 24 450 75 0

Note: For all tests. bicycle wheels were 600mm from edge of the platform and overtakingspeed was 10km/h.

89r Experimental Sof"ty Vehicles Section4. Technical.Sessiozs

Table 3. Cornperable tssts to show the effectl of ground cfaaranceon running over

Ground Number Numbers Numbers clearance Test of runs run over probablyComments (mml fatal Dummyable to roll underguard "550" 1 I 4 3 intopath of wheelsafter falling Dummyfell off guardlater "550" 12 11 3 3 thanTestl. Dummyheld away from path of 300 18 10 O 0 wheelsby bottomrail. Srmilarto Test18 butearlier 300 19 6 0 0 impactPoint on guard. Dummybody restrained by 4OO 23 10 4 0 bottomrail but limbsrun over occasionally. Dummyable to roll underguard 450 24 10 2 2 asTest 1, but hadless time to do so.

For all these tests the guard was in$et by 75rnm, test speed was 10km,/h and bicycle wheels were 6OOmm{rom edge of platform. below it. The tcndencyinstead was for thed unrmyto slide In an attempt to reducethe incidenceand severityof off the end of theguard and be struckby theedge of the impactwith thetyre, as found when testing at position2, leadingtyre. l.heimpact was mademorc scvcrcby the threemodillcations were tested. fact that the dummy could l'all into the 300nrmgap The l'irstmodilication wa$ to curvethe sideguardso betweenthc cnd of'thcguard and thefront of thetyre. In that a srnoothflale was producedbringing the rcar edge Test 2, at 600nrm,l0km/h, and position2, the dummy ofthe guardlevel with theedge of'the plat{orm, as shown was struck by the leadingedge of the tyre in ubout 40 in Figure5b. I'hesecond was a moreirbrupt llaring of the percentof the cases. guard, from about a rnetre from the rear edge of the l-he overall el'lectof speedwas suchthat at the higher guard.again so that it was levelwith the platlormedge. spccdof' l5kmi h, therewas less tirnc for thc durnmyto Ncither ol'thesechanges, when tcstcd at irnpactposition 2 slidedown to the ground and be run over,even when (Tcsts8, 9, 10,and I l) reducedthc incidcnceofhittingthe impact was at position l. However,thc impact with protectingedge of the tyre. It washopcd that theflaring projectionssuch as load restraint hooks and lirtcral l- out of the guard would give irn outwirrtl push to the sectionribcncatl'r thc platform and the tyreswas con- dummy to prcvcntirnpact with the tyre,but, becauseof siderablymere s$vereat the higherspeed. A few runs the300mm gap bctween the end ofthe guardand the tyre, weremade at 20km/h, but thedummy wasdamaged too it still tendedto fall back onto the tyre. frequcntlyand it wasconside rcd impracticable to continue The third modilicationwas t() bring the wholeguard testingat this speed, out levclwitlr theedge of the platform(Tests l4 and l5). At this stagcof the testing,some modificationswere The incidcnceof hittingthe edge of thetyre was reduced madcto thebasic sitleguard to helpdccidc which f'eatures from the original 40 pcrcent to about l0 percentwhen shouldbe incorporatedin theextended guard. tested at position 2, but it was not clear why this Throughoutall the testruns, the shouldcr had tended modilicationwas more e{lectivethan just hlingingout to go betwcen thc top rail of the sideguirrdand the the ru-arcnd of thc guard, platfolrn, the headstriking thc platfornrcdge itsclf, In It wasobvious Irom all thetcsts of thc threemodifica- abouta third of thecases, the shoulder was then struck by tions that further improvementswould be obtainedby eitherthe load restrainthooks or thelateral l-sections to reducing the gap of 300mm betweenthe rear ol tlre whichthey are attilched, To try and redrrcethe incrclence sideguardand thc lront edgeof the semitrailertyre. of strikingthcsc projcctions, a steeltube was positioned It was notcd that in Tcsts 14 and l5 with the whole Iongitudinallyat the.junctionsof thehooks and I-sections guard flush with thc platform edge, the impact of the (Figure 5d), Thc tcsts(12 and l3) showedthat this headwith theplatforrn cdge was not assevere as with the worked well and preventedthe shoulderstriking the inset guard. as well as reducingthe incidenceol' the projections.l'his also resultedin tlredummy not being dunrmy hitting the tyre. This was becausethe shoulder broughtto thcground quite so quickly with a consequently did not traveI as lar undcrthc trailerplatform. slightlyreduced incidence ol runningovcr as shownin Wooden blockswere used to makethe sideguardflush 'I'ablc 3, Test 12. with the platf'ormedgc (Figure 5d), rcsultingin the Experim ental S"fety V ehicle s uprights supportingthe sideguardbeing insetby 95mm SideguardIlprights Inset From the Rails. frorn thc facc ol'the guard.This prcvcntedthe dummy from beingritruck by the uprights.Ihc earliertests had The extended guard was constructed so that the shownthat thc dummy'ship wasstruck occasionally by uprightswould be insetby 95rnm['r'orn the face ol the rails the uprights,which lcd to the dummy bcingthrown off whcn thc guard was flush with the edgcof the platform. the guard soon atter the initial impact. Tcsts l4 and l5 with the insetuprights and rails flush ExtendedSideguard Results with theplatl'orm edgc showed that thc dummy remained in contact with thc guard for a longcl pcriod, which Test condition$ l6 to 22, as shown in Table 2, were lessencdthe probability of it being run over. carried out with the sideguard ground clcaranceat From the resultsol thetests on the basicsidcguard and 300mm. its modifications, an extcnded guard was constructed In the testswhere the sideguardwas flush with the cdge with the followinglcatures. of the platform, thedummy tcndcdto remainupright and came off the end of the guald onto the tyre sidewall,even at impactposition 0. It had beennoted in thcearlier tests Distanceof the SideguardFrom the Ground. with the basicsideguard that the dummy was knocked morc casily to the ground when the guard was inset. One extra rail was addcd to the guard, parallelto the Therelore. somt: tests ( | I, 19, 2 1 and 22)were carricd ground with the semitrailercoupled to the tractorunit. , out with the sideguardinset l}om theplatlorm cdge. In these The ground clearirnccwas adjustableto 300, 400, or runs, which were directly cornparable the tests 450mm.The lowest of thesewas roughly cquivalent to the with carricdout on thebasic sidcguard, as detailcd in'fable 3, minimum allowed rtn coaches.The othcl two distances the incidenceof running over was reduccdto zero. werejust lessand just greaterthan thc dummy shoulder When the dummy f'ellto the ground and rolledtoward width. It washoped that if'th$ground clearancc was less the vchicrlc,it wasprevented l'rorn rolling into path ol' than the shoulderwidth, it rnight prcvcntthe dummy the thc wheelsby the bottom rail. from rolling under thc sideguardoncc it had fallento the Whcn thc sideguard ground. was flush with the platform edge (Tests16, 17,and 20),the resultsconfirmed thc carlier findings from the basic sideguardtests in that the incidcnce of the dummy striking the trailer tyre was Length of the Sideguard ncgligible.In addition,impact with the load restraint hooksand lateral I-sections was less severe, as was impact Thc guardwas e xtended forward as ncar as possible to ol thc durlmy headwith theplatform edge. In thesethree the reirrol'the tractor unit. This wasdonc not only to fill tests,running ovcr occurredin only three instanccs.ln in theobvious gap thlough whichcyclists or pcdestrians eachcase, thc dummywas rult ovcr by therear trailer tyre might lirll but also to give a point of irnpactthat was altcr-coming off the rear cnd of the sideguardand onto furthcr f'orwardthan thoseused in the testswith the basic the sidewallof the Iront trailertyre, sideguard.The earliertcsts had shown that whcn the Test 20, in particular.with the guard flush and the dumnry impactedat the more forward positionon the uprightsnot insct.confirmed thc carlier findings of Tests gr.rard,it wasrnore likcly to be run ovcr.Jhus, an even l4 and I 5 with regardto thcdummy beingknocked to the morcfolwald positionof impactwould bc a hettertest ol' 'fhe ground by the uprights. the effectivenessof the sidcguard, forward extcnsiotr ln Icst 2-1,with the ground clearanceat 400mm, the shouldalso help prcvcnt irnpact with thc hardfront edge dummy wits run ovcl in 4 ol'thc l0 runs,as shown in of the guard, which is othcrwisedilficult to make less 'l'able 3, but 3 of thesecascs were relativcly less serious in injurious. nature.involving cither arr alm or a leg. The rear ofthe sidcguardwas extendcd to beas close as With thc ground clearanccat 450mm(Table 3, Test possibleto thetrailer tyrc to testwhether it would prevent 24),running over occurred [wicc, and thesec-ascs involved the dutnmy striking the lorward edgeof the tyrc. either the dummy heaclor trunk.

Distanceof the SideguardFrom the Edgeof thePlatform AcceptableGround Clearancesfor Sideguards 'fhe Three of the nine tests on the extendedguard were results shown in this paper indicate that if the carricdout with theguard flush with theplattorm edgc as ground clearanccof the sicleguardcould be rcducedto this was shown to be beneficialin the earliertcsts, The ahout 3(X)rnrn.the incidenccof running ovcr woulcl be remainingtests were donc with theguard insct at various negligible.lt no doubt will be arguedthat sucha low distanccsfrorn the edge. clearanceis not acceptableto opcratorsof I-I(iV's even

8q4 ' Section 4, Technfual5essiozs though an equivalentground clearancedoes appear to be serious injuries at closing speedsup to about acceptableto crlachoperators. Increasing the clearance 6-5km/h provided they are wearingseatbelts to to 400mmgives nearly as good results. and it is interesting thc lirtcst spccil'icirtionsand the car interior is to notethat, sincel9tl0, goods vchicles in Japan(5)have sufficiently spacious forward of the front required sideguardswith a maxirnum ground clearance ccupants. of 450mm.From observationol'the vchiclcsin .lapan, lhc bumper absorbs approximately 20kJ of eventhe largestarticulated vehicles often have clearirnces impactenergy by deformingsteel tubes using the of 380 to 400mm without obviousopcrating difficulties. invcrtubcprinciple. Thc bumperweighs about 60kgand would probablycost about f 150r'etail. Thisis only slightlymore than thc cstirnatcd cost Severityof Injury to Two-Wheelertlsers and Pedestrians of an adequate rigid (that is, non-crlcrgy- absorbing)guard. No attempt has been made in this paper to estimate 3. ln vicw ol'the benefitsin reducedcar occupant severity of injury exceptto distinguishbetween obviously dcathsand injuriesthat would resultfrom the fatal injurieswhen the heador trunk of the durnml'was useof energy-absorbingfront undcrrunbumpers run over by thc trailcr whcclsand the relativelyless on trucks,it issuggcstcd that an1'l'rrturc lcgislation seriousinjuries cau$ed by running over limbs. for theseguards bc basedon rcquiringatr agreed someof the impactsof the dummy with Qualitatively! capabilityto absorbcncrgy ratl'rcr than specilyirtg the leadingtrailcr tyrc and the headwith the platform ''l a minimum strength.A possiblelegislative test edge appearcdto be vcry severc. his was particularly procedure I'or energy-absorbingbumpers has truc with the insetguard. Il is hopedin thc ncarl'uture to beenerutlined using an itnpactorwith a rigidlirce carryout sometests with an instrumentedOPAT dummy perhaps 200mm squart:,weighing 200kg, and to estimatethe severityof likely injury causedby such hitting thc burripcrat 50km/h^ The maximum lmpacts. allowabledeforrnation of thc burnperand the maximum lorce experiencedby it would be AlternativeSideguards limitcd, provisionallyto 400mm and 200kN, respectively. The presentpaper deals only with sideguardsmade The almostunive rsal we aring of seatbeltsin the up of uprights supporting Iongitudinal rails. Where l)nitcd Kingdonr makcs it worthwhile to lit accessbeneath or to the sideol the vehicleor traileris undcrrun burnpersgiving this performance.In necessary.this rnaybe a scnsiblcchoice of construction. countrieswhere seatbclts are rarclyworn, thcre Howevcr, on trailersor semitrailerswhere this accessis may be Iittlc.justificationfor undcrrutrburnpers lessimportant, other types ol constructioncould be used. to prevcntintrusion into occupantsat relirtive An obviousalternative is a skinnecJsideguard using a spcedsntuc:h above 4Okrttr h. Iightweightfrarne covcred with alurninumor a glass- 5. Further testsare plannedwith both the truck reirrforcedplastic strect. On platform-typetrailers, solne and car moving to confirm that the underrun ingenuitycould be requiredto overcomethe problemof guard is effectivein theseconditions. accessto re$trainthooks. but this lorm of'corrstruction Work is in hand to investigatcthc l'casibilityof would presenta $moothersurface for the cyclist or {ittingguards to modernHLiV's. pedestrianto fall against. From work donc on [IGV aerodynamics,it hasbcen shown this type of sideguardwould also give reduced Sidegunrds aerodynamic drag, a definite bonus f

895 E xp erimental Safety Ve hicles

and the leading trailer tyre, the pedal cyclist Acknowledgments could bc stluck scverelyby the leadingedge of the front trailertyre. The work described in this paper forms part of the I)ue alsoto theguard being inset, the head of programme of the Transport and Road Research the cyclist could severelystrike the platform l,ahoratory, and the paperis published edge. by permissionof the Director. Thanksare due to Mr. M. pageof TI Tube The pedal cyclist was more likely to be run Products I.td. for his cooperationin the programmeof over by the trailer wheelsat thc lowesttest srrccd work prcscntedin this paper. usedof l0km7h than at highcr speeds. With a sideguardextended rearward to becloser to the trailer tyre and brought out flush with the References platlorm cdgc and having a reducedground clearance,the performance of the guard was l. Riley, 8,S,,and H.J. Bates,',Fatalaccidents in Great improved as follows. Britain in 1976 involving heavy goods vehiclcs," With a unifbrrrrground clearance of 300mm, Department of the Environment, Departmcnr of the incidenceol' r-unningovcr wersreduced to Transport, TRRL SupplementaryReport SR 5g6, zero. At ground clearances ol'400 ancl45()mrn, Crowthorne,Transport and Road ResearchLabora- the incidenceof running over increasetlslightly. tory, 1980. Thc incidcnceofthe pedal cyclistbeing struck 2. Riley,8.S., B.P. Chinn, and H.J. Bates,..Ananalysis by the edge oI the lcading trailer tyre was of latalities in heavy goods vehiclc accidents," considerablyreduced. Department of the Environment, Dcpartrnent of The severity with which the dummy head Transport, TRRL Report LR 1033,Crowthorne. struck the platform edge appearedalso to be Transport and Road ResearchLaboratory, l9gl. reduced, "Strucrures, 3. EEVC Working Ciroup6, improvedside Insetting the uprights from the rails of the impact protection in Europe," proceedingsNinth guardprevented the dummy lrom bcingknockcd InternationalTechnical Conference on Exrrcrimental to the ground by the uprights. SafetyVehicles, Kyoto, NHTSA, U.S.Departmcnt The forward extensionof thesicleguard would of l ransportation,1982, reducethe possibiliry of falling in front of the 4. Motol Vchicles(Clonstruction and [Jse)(Amendment) guard or onto the hard I'rontcdge. (No. 7) Regularions1982, Regulations468 (in- J. The procedure describedin this paper could corporating Council l)irecrive 70I ZZI IEEC), 4(iC. form thc basisfor thedevelopment of a standard and 46D. test to evaluate the effcctivcncss of future 5. AutonrobileType Approval Handbook for Japanese sideguards. Certification,Effective Date: August 20, lgg0.

Load Restraint for the Protection of Occupantsin Light VansIncluding Car Derivatives

D.G.C. Baconand restraint manufacturers,and racking manufacturers. I. Gazeley In an informationgathering phase , thetype of accirJents The Motor Industry Research wcredefincd against which the restraintsystcm would be Association 'l-he required to provide protection. speciliedaccidents weresimulated using barricr crashtests anrJ dynamic sled Abstract tests.The testvehicles were equipped lyith bulkheadsand storagebin systems.Virrious schemes of loatlswere held down with webbing restraintsattached to anchorage The problems of restrainingmiscellaneous loads in points. This test work, as well as providing the loading light vans and passengercars derivates quantified were inf'ormationf or the restraintspecification, also indicated with a view to developing specifications for strong thc performanccgivcn by existingsystems. Specifications anchorage points, bulkheads, racking, and restraint for cargo restraint$ystems were drawn up and prororype systems.The projectbrought togcther the main organisa_ designs engineered to this standard for evaluation. tionsinvolved: the fleetopcrators, vehicle manufacturers. Performancetests were carried out on the overallsvstems

896 Section4. Technical.Tessmzs to cover the different conditions and types of load Survey of Fleet Operators'Accident experiencedin service. Reports Thc I'inalstage of the project involvedpreparation of the dctailed spccil'icirtionsfor the anchorirgepoints, A search was made through the records of four fleet bulkheads, racking systems,and restraintsthat would operatorsto determinethe number ol accidentsinvolving form part ol'a RecommendedPractice. frontal impacts irnd the rangc of impact speeds.The combincd numbcr of vehiclcs opsrated by the organisa- tionsamounted to approximately15,000, and the search Introduction covereda 5-yearperiod. Sideand reirrimpacts were not consideredsincc it wasfclt thesetypes of impactswould The light van is one of the mostwidespread vehicles on not propel unrestraincd loads toward the occupant the roads today, Passengercar derivatives and the compartment.The accidentrcports studied did not refer forward contr'olvans. which forrn the two main groups, to displaccmentof cargo,The invcstigationslooked at a are usedby thc thousandsfor carryinglight loads. total of 303 vchicles that w$re in rnotion when the It is, of ceurse, oftcn nccessaryto restrainthe load accidentsoccurred. within the van, This is ncedcdfor the protectionof the The obstaclesthat the vehiclescollided with were front-seatoccu pants and sometimesfor thc preventionof categorisedand are shown in Table l, damage to thc load itsclf, Indccd, sornetitncsit is necessaryjust to prevcntthe loadfrom becomingmixed Table 1, Obstaclesencountered by vans from a survey by the ffiotion of the vchicle.For all thesereasons! a of fleet accidents varietyof load restraintsystems has bee n developed.The maln onesare..- Cars 218 r tlulkhcads,intcndcd to providcoccupant protcc- Roadsidefurniture 33 tion bv holding back the lond Heavycommercials 23 and cyclists 11 r Racks. used with containersinto which loose Motorcycle$ Farmmachinery I gathered tools and other srnallitems carr he Buildings 4 r Webbing restraints, used to anchorheavy loads Others 6 of a variablerlature r Clamps, used to hold down heavy items of a predetcrminedkind, suchas trolleyjacks The distribution of the number of vehiclesrelative to The need I'or such systemsis l'elt particularly by the impactspeed is shownin Figurel. Taking into account major national organisationswho operatelarge fleets. that the majority of impactsinvolved another car and 95 Such organisationsoperate in a nrore systematicway percentof the accidentswere at speedsless than 64km/ h than the smalloperator and placea greateremphasis on (40mph),then this information providcd thc guidance for sal'eoperation. the speed to bc used in the c'rashtests with a rigid ln fitting out their vansfor variouspurposes, the major nondelormablebarrier carried out in this project.In national fleets found they faced a common problem. vehicle-to-vehicleimpacts, thc equivalentbarrier impact There wereno estatrlishedfixing pointswithin the backof speedcan be considoredto be approximately half the thc van to which the fleetengineers could attachtheir vehiclespeed. Thcrcfore, in this work an impactspeed of systems.All sorts oi methods were improvisedfor 32km1h (20mph)was cmploved to covcrthc majorityof overcomingthis difficulty, and pickup pointswere devised accidentcircumstances in frontal impacts. on an ad hoc basis,It wasconsiderably more difficult to add strong ancholergcpoints aftcr thc vchicle was TestProcedures completcdthan it would have beenin the courseof manufacture.Iiurthermore, the cngineersof thc vehicle manufacturer wor.rldhave been far better placedto decide suitable locations and designs.Finally, there was no CrsshSimulation Testing on the HYGE control over the strerrgthof theseanchorages. If they weredesigncd into the vehicle,instead ol beingadded on To carry out a typical test series,a van floorpan or an ad hoc basis,thcy could havehad a specifiedstrength, bodyshellwas securedto the HYGE sled through its The project dcscribedin this paper brought together suspensionmounting points by a purpose-built rigid the main organisationsinvolved, that is. the I'leet frame. Particularattention was paid to making ccrtain operators,vehicle manufacturers, rcstraint maltul'acturers, that it waswell secured in viewof thenumber of dynamic and rackingrnanulhcturers. They steereda programme teststo which it would be subjected,The van would then of test work, analysis, and assessmentto provide a be kitted out with the appropriateload of equipmentfor a consensusspecification for light van restraintsystems. test. Carnerasrequired for filming movementof objccts Experimental Safety Vehicles

SAHPLE

aJ1 l! J TJ E r.r.J

o E LIJ (D E f =

mite/ h

6/+ OVERkm/h II.4PAITSPEED 6l- '1 Figure . Number of vehicles involved in accidents in specified speed ranges

during the test were positioncd on the sled and instrumentation transduccrsattacherl to record forces and accelerations.The sledwith the bodyshellmountcd on it wasthen accelerated backward by tiringthe IIy(i H, thr-rssimulating a lirrward dccclerationimpact. Instrur.ncnta- tion and Iilnr analysiswere then carricd out to assessthe resultsol lhe test. Figures 2 and -1show views of typical floorpan and bodyshcllinstallations before a test.

Figure 3. Van bodysholl tost on the HYGE, showing equipment carriedand storage bin system on vehicleside

Barrier Crash Testing

In preparationofa van for a typical load restrainttest. large aperture$wct"e cut in the van side to give good photographic coverageof the movcment of the cargo Figure 2. Van floorplan test on the HYGE. showing inside. tJsually some light cross-bracingwas welded equipment carried and webbing restraints acrossthe apertures to maintainthe stiffnessofthe bodv.

898 ^Section4. Technical Sessions

Any racking or storagebin systemwould he fitted to the main function is to preventloose objects sliding or flying oppositcside that had not beencut. forward to causedarnagc or injury. Existingbulkhcads areconstructcd I'rom various sheet or meshmaterials and Static Load Testing are attachedto the van sides,roof, and floor by a variety of means.Figure 3 shows a typical ad hoc timber and meshbulkhead. Testswerc carricd out with a floorplanof the vehicle Thecxistirrg Swedish regulation for bulkheads,SS2562, bolted to a channcl sectionsubframe. Shackles were providcd an immediatelyavailable specification, which installedinto the lloor anchorage,irnd thcn a load was wasassesscd to seeif it matchedthe requirements of these applicdat a specilicanglc by mcansof a hydraulicram investigation and a chain, A vicw after onc of the testscan be seenin Figure 4. Bulkhead Test Progrf,mme

The majority of bulkhead tests were carried out in vehiclebodyshells in ttrc'-bodyin white"conditionon the HYCE, Variousitems ol cargowere left loose in theback, which thcn moved l.orwardto strikethe bulkhead.Srnall itemsof high rnass,such as a trolleyjack, wereused to givca conccntratcdload that couldcause problerls with somcdesigns of bulkhead. In addition,bulkheads were assessed in the programme of full-scalccrash tests that involvedimoact from similar items of cargo, Figure 4. Static load anchoragetsst using van floorplan

Road ManoeuvreTesting Bulkheads- Summaryof Findings

practicable A seriesof braking testswere performed to evaluatethe It was not to view the bulkheadas a retentionof storagehin systems.This work wasI'ollowed restraintdevice capable ofstopping all loadscarried up to by corneringtests that involvedd riving the vanat various the maximum capacityof the van and at all possible speeds. speedsaround a constant radius to induce lateral impact A tnaximurn load would havc to be accelerations specified that could be allowed to come loose rn an irlpact and also a maximum velocity at which the bulkheadwas capablc of stoppingsuch a load.This load TestProgramme and vclocity would bc relativelysmall compared with the maximum payload and thc rnaximum speedthe van dcscriptionof test given An outlinc the programmeis could rcach.This meant the remainingcargo of the van in Tablc 2. Full detailsol'the tests and their resultshave should be adequatcly rcstlaincd to floor anchorage published MIRA bcen in a report(l). points.Information l'rom other parts ol'the project were brought in to provideguidelincs for the looseload and Bulkheads impactvelocity. I n a surveyof typical storagebin contentsofvans, load Bulkheadsprovide a divisionbetween the load-carrying valuesol about l lOkgwere found for a 900kgpayload -l area of the van and thc occupantcompartment. heir vehicle.Tl're accident survey sl'rowed that rln equivalcnt

Table2. Loadrestraint test programms

Evaluating Type o{ Test No. of Speed Vehicle Tests km,uh State Bulk- Anchor- Storage heads ages Bins Restraint i r Barrier lmPact 4 32 Whole van r * * Hyge Sled 23 16-40 Bodyshell + Hyge Sled B 16-40 Floorpan t * * * StaticPull 14 Floorpan Braking 6 20-6O Whole van * Cornering I 20-90 Whole van *

899 Experimental Sof"ty Vehicles

barricr impact speedof about 3Zkm/h (20mph)covered was often in doubt, and in most casesit was not known most of the crashesseen on thc roads. how strongthey should 'l'hese be anyway. figuresol I I Okgat 32km/ h seemeda reasonable It was c:onsidcrcdmore di{'l'icultto add anchorage targct for thc performanccof a bulkhcadfor that sizevan, points after the vehiclc had been rlanufactured,and it and thc sled and crash testsindicated some currenr wasmore appropriatcfor themto beincorporated during designsof bulkheadswcre capablc of withstandingthat vehiclebuild. Also the manulacturers'designerswould type of impact.lt alsoseerned reasonable that vanswith havemore inlrlrrnationto enginccrthe requir.cd strengths. higher payloadsshould have strongerbulkheads and Hrlwever,thc positionsand numberol thcseanchorages smallervans lessstrong bLrlkheads. would be very much inl'luencedby thc experienccof the This philosophywas part of theSwedish regulation on flcet operatorsin their day-to-dayusage of the vans. 'I'he bulkhcadswhich specilicda rangeol'impact energy {'or main task wasto decidewhat wasexpccted of a bulkheadsto withstand.based on vehiclemaximum load anchorage,in telms of wherethcy would bc located payload.This energyspecillcation has been intcrpreted in within thc van,and what would beattached to them.'fhe termsof loosepayload and irnpactvclocity in Tablcj. lt questionol how many anchorirgcsshould be provider:l in can be seen that for the 900kg van, the unrestrained a van wasalso addressed and whether this numhsr varied payloadis 90kgat 32km/h. with thc sizeof the virn

Table3'Permissible unrestrained payloads impacting bulkheads at differentvelocities in accordancewith swedish standardss2s6z for varioussize vehicles

UnrestrainedPavloads

Unrestrained Payload lmpact lmpact lmpact lmpact lmpact Sizeof Permissible at at at at at Vehicle EnergyLevel 16km/h 24km/h 32km/h 4Okm,zh 48km./h Payload (Joules) l Omph 15mph ZOmph 25mph 3Omph

25Okg 1000 10okg 45kg 25kg 16kg 11kg 40Okg 1600 160kg 71kg 40kg 26kg 18kg 900ks 3600 36Okg 16okg 90kg 58kg 4okg 2,000k9 8000 8O0kg 356k9 200k9 128kg 88kg

The main requirementsof the Swedishregulation in Load Anchorages-Purposessnd Locations relirtionto bLrlkheadswerc adopted as the specilication or RcconrrnencJeclPractice resulting from this pro.ject.This Thc had thc considerablebcnefit ol' a comrnonrccluirement fleet operators'expericnceshowed there was a for vehiclemanufacturers tLr mccr. dual function requirementfor floor anchoragcsand thcre was also a needl'ol anchoragcs However,atterrtion was drirwn to a desirableaddition at a high levelin the van. Thc floor anchoragcs to thestandard lclating to thc preventionof smallobjects had to bc sutllcicntlynumcrous to allowconve nicnt lashing cargo passingthrough mcsh-typebulkheads in thc vicinityof of at mostpositions on the dlivcr'shcad. thc load-carryingarca, though it was consitleredmore probahlcthat thislashing would take placc at therear end of thc vchicle becauscit was rnore accessibleto the opcrator. f'hereforc, in delining an arrangcmentof Load Anchorages anchoragepoints l'or the largervans, more points have becn put at the vehiclerear. It was also evidcnt that ir A load anchorageis a strongpoint on the van floor or lalge proportion of these I'lect vehiclcshave installed sidesto which itemsol'calgo can bc attached.'l'heload side-mountcdracking systems with storagcbins. Thcse anchoragewill havc a delincd capacityunder cerrarn systernsrequire attachmentfor the fcct of thc louvred loadingconditions, which will mcanthe item of cargocan pancls to the vehiclefloor. To keep the number of be restririnedup to a spccificdlevel of irnpactsevcnry. anchoragesdown, it was decidedthat thoscalong the 1'hcproblem for thc fleetopcrators had hccn that until sidcsof the lloor should havcir dual function of lashing recentlymost vansdid not havecstablished anchorage point and rack-mountingpoint. points. To attach restraintsor rirckingsystent$ required The siclc-mountedracks require an upperfixing point, thc improvisationol drilled holesand attachmentof whichis usually thc vehicle cant rail (or similarstructure) rcinforcingplates. The strengthof thcscarrangemcnts to attach the top of the rack. As the racking systemis Section4. Technical,Sessfons vertical (or nearly vertical), this upper fixing point be restrainedin thesesimulated impacts was provided by definesthe laterallocation of thefloor anchoragesalong the fleet operators.Fllectronic lorce transducerswcre the side of the f'lottr. attachedto the webbingrcstraints ttt recordthe tcnsilc In summary,thc anchoragelocations in the floor were loads in each rutr ol webbing.Figure 5 showstypical planncdas a row on eachside at a lateralspacing dictated loads measured,From theserecords, it was possibleto the by the upper fixing points and a row on the vchicle establishthc loadvariation on cachanchorage during centreline biassedtoward the vehicle rear, The uppcr test and also thc uraxintumvaluc tirat occurred. anchoragcpoints consistedof a rolv on cach sidc in the cant rail.

Types of Load Anchorage RH Y€TTII6 for a singie-loadanchorage or attach- Variousclesigns 2l ki lh ment point were examined,Somc rll thesewere sintple l5;itclh but difficult to use,and othcrswcrc complexin design with usefulleatures but quitc costlyto incorporate.The intcntion wasto tind a suitabledesign that wasacceptable to both the lleet operatoratrd van manulircturerwhile still mcctinga spccifiedload conditron. The variantsbased on thc 7, l6in UNI'-threadcdhole 'fhe were nlore attractivefor sel'eralreasons. concept of restraint an anchoragebcing a reinlorced7i l6in IJNF-threaded Figure 5. Loads measured in webbing holc is widely accepted in the field of vchiclesalety belts. Alsothis design allows the addition of, say, the attachment of a brackctfor rackingsy$tcllrs as well as the link for the Static Tests load restraint, The 7/ l6in UNF-thread$d hole as an anchoragewas adoptedl'ttr lloor anchorages. The aims of the programme were to achievesimilar The van manufactursrsfound this type ofanchorage anchoragcdelormations in thc staticpull test and thc could he incorporatcdin thc vehicle build without equivalcntdynamic test to discoverthe staticforce that extensivetooling changes. Consequently, thcsc anchorages woulddestroy thc anchorages and to establisha stirndard were fairly inexpensiveand had a high probabilityof $tatic test of lorce against a timc period tor testing actually being offered as an option (or as standard anchoragcswithout havitrgto lcly on dynamictesting. equipment). that the upperfixing pointscould bea It wasdecidcd Dynamic/ StaticComparison simplehole or any otherconnection detail at thed iscretion manulactureras long as it mct the strength of the The grcatestloads of about 20kN weremeasured in Howevtr.to avoidany elementol doubtabout criterion. restraininga l25kg generatorin simulated40krn/ h dctails. it was preferredthat this upper reinforcement (25mph) crashes.This payload was considcrcdto be point should again be a threadedhole but ol a fixing typical of some of' the heavieritems usedby thc l'leet than thc l'looranchorages (and seatbelt smallerdiamctcr operators in their vans, atrd, if it could be restraitred ln this caliera t'tretricthread ot i'lmm was anchorages). succcssl'ullyby the anchoragesystem, it would rcpt'esent as the standard. chosen a suitablestandard to achieve. l-he floor d istortioncirused by dynamicloads of 20kN Floor Load Anchorages-Test Programme wasreproduccd in statictests by loadsof about l5kN that were of much longel durirtion.This observatiorrfollows other experienccsin impactstudies otr stcclstructures, DynamicTests which show a dynamicamplil'ication factor with higher velocities. The aim of this programmewas to establishthe l'hc outcomeof thisexercise was the establishment of dynamicloading of floor anchoragesunder typical the strengthrequirement o1' I'loclr anchorages at l5kN' contlitionsol'payload and impactsevcrity. These data The anglc ol' load applicationwas specifiedto bc 30o, would providethe guidelincsfor the speciticationof which was cotrsistctrtwith typicill lashingangles i'or anchoragestrength in termsof a staticpull test. cargo.A minimunrload application timc ol'0.2swas also A sericsol' sled testswere performedusing van specifiedto be consistentwith similartests on $eatbelt floorpanson the HYGE sled. A rangeof iternsof carSo to anchorages(l-igure 6).

90r Experimental Safety Vehicles

maxlmum payload. Rounded values of upper fixing point load for both sidesof the van werecalculated as follows: - 250to 400kgpaytoad 4.0kN 900kg payload o 9.0kN 2t payload 20.0kN A forrrrulationbased on payloadwas put forwardfor the strer-rgthof the upper fixing points.

Figure6. Typical Floor AnchorageLocations static loads appliedto floor anchor_ i ages meeting strength requirement 'Ihe anchoragepoint layout for a light van (short wheclbasc) wasclesigned to suitfleet up*rutorr,n.eds and Upper Fixing Points-Test is show,nin Figure Evaluation and 7. l-or longervehicics, it couldbe scen Results that an additionalanchoragc would herequired on each sicieand in the rniddle.This irspectis cover.cdby the The attachmentof Recommendcdpractice storagcbin systemswas usually as a I.unctionof loading irrea straight onto thc upperfixing points,ancl the measureme't lcngth. o[ forcesac-ting at thescpoints I'he anchorage could not be nrcasured .. point layout for car derivativevans dircctly. The rncthorj usedwa.s to take a valuc for (he l'ollowedsimilar principrcs. decelcration ol' the van in an itnpact, wtrrch, with knowlcdgeof the massof'the storage bin system,would StorageBin Systems give a value to the for-ceacnng. This information ledto considerationof the strength of Racking sy:itemsin vans provide thc upperanchorage I'ixing points storage lrins of asa I unctiono{ thevan vanous capacities(usually 5, 10, and l5kg) that are

,*-_J-

.s /fi7*yo (F -7t -. FT,a veHxHICLECENTRE LINE q t' r'..",,,r') -Tt a #--r O t- O o E 'zoNE pLActN6 E rn FoR sTRoN6ANtHoRA6ES - F E TYPttALDtMENSt0NS SH0h/N tN O mm z, J

:1_ - swEDtSHRE6 MAX REFEREN.E'LANE t venircnrLy- aEl0w-cnr,ppa- :zlb I orrroo*o ZONE T Figure 7. Floor-mounted anchorage zones for lt payload vans

902 S ection4. Technical.9essrozs hooked onto pressedsteel-louvred panels. Two systems detachedfrom the louvred panelsand flcw forward to matle by dif[erent manufacturerswere assessedin this strikethe van bulkhead. project. Both werc bascdon wall-mountedassemblies A rnajorconccrn was that evcn if a methodwas devised that werc usedtnainly in workshtrpsfor storagcol small to retainthe bins,the bin contentsmay comcout and still items suchas nuts and bolts.The louvred panclsolfered becomea hazirrd. flexibility in the positionthat a bin could beattached, and It wasconcluded that if binsand contentswould come it was common practiceto unhook a bin ol'necessary loosein an impact,the hulkheirdwould haveto bc the compontlntsand takc it to wherea job was beingdone' prime protectivedevicc. However, bulkheads will only Figure 3 showsa typical stL)ragebin systcm. withstand a specifiedrange of impact cnergy basedon Although this projcct concentratedtnainly on the vehiclemaximum pat'load.This meant the maximum storagcbini louvrcdpanel system, racking and shelving unrestraincdpayloads tor differentimpact speeds would constructedfrom slottedangle is also widcly used by flcet beas givctr in'I-ablc -1. Therefore, thc Inaximumwcight ol operators.l-he Ilain requirementfor thistype of racking unrestrainedbirts and contentsthat couldbe carried rn a is strongattirchment points, and it would bethe intention van would bc givenbv the32kmi h colutntr.c.g',90kg for that the anchoragesspecified in this work would be a 900kgpayload vehicle. This becamethe basisfor the employedfor thesefittings as well. maximutnpcrnrissiblc loading ol'a storagebin systent'

StorageBin Systems-TestProgramme RestraintSystems

ImpactTests This section rclates to the various fittings such as shacklesand D-links,together with webbingharncsses, of sled testsemploying van bodyshells The majority ropes,or chainsthat connect tlre cargo to theanchorages I'ull-scalcvan critsh testscarried storagebin and all in lhc load floor. out with a varicty of hins and hin-loading systcmsfitted Lvery tcst carried out in this proiectwith a restraincd schemes, item of cargoemployed some typc ol'restraintsystcm. It wasapparent from the veryfirst testcarried out with Thereforc, many rcstraint componcntswere proved in loadcdbins at l6krnI h that they bccomedetached fully thc asscssmentof othcr sYStelns. louvred panels.A repeattcst with partially from the Havingdccided on a strengthspccilication of I5kNIor bins(about 50 percent)still showcdbin separation loaded the load anchoragc,this automatically set the trrinirnum the panels. frorn standard for all other componentsin the load path. it was realised that in almost every impact Oncc Howcver,in lincwith workingpractices for thcsesystellls, thc binswould leave the parrels, most of the circumstance a percerltageoverload was desirablc thiswas set at 33 the strength of bulkheadsalso included testsassessing pcrcentgiving a restrainttest load of 20kN. someloaded bins, l'his criteriacan be met by chains,wire roPes,rope, or 'l syntheticwcbbing. helutter was the material used in the Road ManoeuvreTests testsand provedvery suitahlc.It is eirsyto Llsc,absortrs muc,hof thc d1'nanticforcc, and doestrot ciruse secotrdary programmswas initiatedwith a van fitted A small test damageto the cargo. involvedstandard hard out with a storagebin systemand Excrciseswcre also carried out in lashing itcms of braking and corncringtests' cargo to the anchoragelayttut specifiedfor a variet)'of could concludedthat despite some LJnderbraking. it be van floors.ln an earlyvchicle test, it waslrlo$t noticeable remainedon thcpanels smallforward movement, all bins that. in a forward collisionor severebraking condition, Averageaccelerationsduring and retainedtheir contents. the cargoattempts to movevertically and, i{ insufficient I hevalue, I '0g.was used thesetcsts did not exceedL0g. vertiL:alrestraint is applicd,it is possiblcfor the cargoto in spccil'yingthe longitudinalload test for bins. riseand roll over the horizontal rcstraint. During cornering,the testsshowed that all binswerc retainedby the Iouvredpanels up to tht:maximum lateral accelcrationof 0.7g. Only small items were displaced Conclusion from a small bin at accclerationsof 0.549and above.ln 'This the main organisations this work, the valueol l.0g wasadopted lor thc lateral project brought together thetransportati(ln oIcargo in load tcst specificationfor bins. involvcdin theproblems of vans. gatheredfrom I'leetoperators to StorageBin Systems-Summary of Findings lnlormation was thc provide background data for the performanceol' the bin systems. ln almost every impact test ol racking systemsfitted bulkheads, load anchorages,and storage itcms carried in with bins,Ioadcd to a varietyof schemes,the binsbecame This not only establishedthe range of

903 Experiment al Sofety Ve h icle s

vans but also involved the definition of the type of they nor be usedwithout a bulkheadbeing fitted incident againstwhich the systems must hold the fitted to the van. The capacity equipment. of thestor.age bin system should be limited to what the bulkhead Simulation of the incidents, can which included vehicle contain in an accident. collision, emergencybraking, and cornering, fcrrmeda r Restraint systems major part such as chains, ropes, or of the testprogramme that providedthc data synthctic webbing can be used to connect the to quantify the prohlems ol' restraining miscellaneous cargoto the strong loads. anchoragesin the load floor. This enabledspecil'ications to bs drawn up and It is a requirementthat all componentsin the assesscdagainst a backgroundof realisticinformation. load path should withstanda loatl of 20kN. Some ol the more important conclusions of the work As a conclusionto theproject, are as follows: thevarious specifications devcloped in the course of the work wire r Injury from loose brousht objectsmay be preventedby togcther in a Recommendedpractice(l). fitting an impact-re$istantbulkhead between the load-carryingarea of the van and the occupant compartmcnt. Acknowledgments Typically, sucha bulkheadfitted , in a 900kg payload van will stop unrestrained objectsof 90kg moving at 3Zkm/h (20mph). The authors would like to thank the following r organisations Fleetoperators require strong anchorage points for their contributionsto this work: U.K. Department 'l'rade to be installedin thc floor of thevan socargo can of and Inclustry, Austin Rover, Automohile be restrained.A static load criteritln has been Association,British Oas Council, British Rail, Dcxion, specifiedfor thescanchorages as a rcsult oI.the ElectricityCouncil, Ford Motor Company, Linvar, Spanset, testsin this work. The strengthrequirerl is a load and Tyrite.Additional financial,uppo.i was of l5kN at an angleof 30.. Anchoragesshould given Irom the MIRA (ieneral Fund. , consist of 7l16 UNF_threadedholes in an arrangement that is a function of load lloor References length. Strong anchoragesare also requiredat a hieher L Bacon, D.G.C., J.A. Searle,and I. Gazeley,-.The levelin the van for the attachmentof ttretqt of restraint of loads in light vans," MlRn racking systems. The preferred Report, form of these Novenrher1984, anchorages is an [imm threadedhole. 2. ,.Recommended MIRA Projcct Group, practicefor The performance of side-mounteclstorage bins restrainingloads in light vans."MIRA publication, wasassessed and, asa result,it wasrecommcnded April 1985.

SevereCosch Accident Survev

C. Thomas, priorities that designersand manufacturersneed to F. Hartemflnn,and considerin Iuture vehicles.Despite thc good safetylevel C. Tarriere of coaches,some spectacular accidents ncvertheless occur l,aboratory of Physiologyand Biomechanics causingscrious injuries and de*th to the users,ancl these of arc often PeugeotSA/ Renault (France) brought to the public'sattention by the media. Thit survey is basedon all the fatal coachacciclents .l.he P. Botto, that occurred in France bctween lgTg irnd t9g4. C. Got, and paper describcsthe causesand accidcntconi.igurations A. Patel and analyzesthe injury mechanisms.Countermeasures arediscussed, and possibleways of.minimizing OrthopaedicResearch I nstitute, occupant injuries.relatl:d to strengthol f'rontend strucrures, HospitalRaymond poincare seat (France) back improvements,window retention,and i.ircprotec_ tion, arc suggested. Abstract Introduction Data about severecoach ac.ia.nts are still limited. During eachof the past More knowledgein l0 yearsin France,32 people thisfield is requiredto definesafety were killcd and 162 seriously iniured on averagein

904 Section4. Technical.lesslozs

where the coachesand buses.Coach accident victims represent only accidents occurring on the road network (the French net- 0.2 percentof the total of roarJaccident victims' GendarmerieNationale opcrate entirc motor- Table I shows for 1984the nuurber of deaths and work cxceptmajor conurbationsand suburban (January l, 1978' to serious injuries among rnotorizedroad users,together ways) during a 7-year period with an cstimateof uscr kilometersand the fatality rate December31, 1984). (empty )8'000kg for eachmode. All vehiclcswere large buses weight: and 40 passerlgersor more) exeept six were bLlsettes Table 1. Road transportcasualties in Francein 1984 (emptyweight; )4.000kg and 30to 39passcngers)' Cases involvirtgsmall buses or city buseswere climinated from DeathsPer the sample. Krlled SeriouslyThousand Million and studiedat the Inlured Userkrns The accidentreports were collated ParisHeadquarters of the Cendarmeric trytwo accident 1 452 5 in particular, provide in- 8us andcoach B -1"12 0 anillysts. These docrrments, Truck 165 6 'l formation cttncerningthe generalcircumstances of'the Car 7,11 39,930 16 accident,the siteplan, intcrviewswith thoseinvolved, the Mopedand aswell as photographs ol' motr:rcycle 1,684 15,238 100 seriousnesso1'victims'injuries, vchiclesinvolved. In thc case of l4 accidents,a much deeperanalysis It is clearthat the fatality rate ofcoach and bususers is performerl by our laboratory enabledthe police-based very much lower than that of any other means of inlbrmationto be comPletncnted. travelingby road, However.action to minimizefuture similar occurrences, where possibls,is in the handseither of designersand Active SafetYAsPects manufacturers or legislators. Real-life accident dirta ovcrviews are needed to help them rationalize new According to the police data(S),the extent of coach improvementstor coach safety.Few studieshave been driverblameworthincss in all personalinjury accidents is publishedon this matter, fortunatelyvery low (only ,30percent). But, in the latal Baxtcr(l) discusscdsome of the problemsassociated accidentsample, this rateis 2.5timcs highe r (73perce nt) 'l'his with coachesinvolved in rollover-typcaccidents and than the fornter. highlightsthe importanceof the proposeda minimum standardfor the strengthclf coach coach driver in accidentswhere there is at least one structurss. occupantdeath. This high degreeof presumedblame- Stansifer and Romberg(2) conducted a cost-benefit worthinesssllould be rclatedto the fact that, in l8 cases analysisofsafety belts based on 66intercity bus accidents. out ot 48 (38 percent),the coach is the only vehicle Theyconcluded that a rcquirementto fit safetybelts at all involved. seats in coachesshould not be recommended.This Accidentsoften havemany causes.The distributionof conclusicn is also supportedby frontal impact test main apparcntcauses of the 35 accidcntsin which the findings(3) that demonstratcdlapbelts could do more blanrcworthincssof tlre drivcr seemsclear-cut is shown harrl than gooddue to harderhead irlpacts against scat below: backs. Davies(4)analyzed I I schoolbus crashesin Ontario. Loss of control on a bend 6 of on black ice 5 The author mentionedthat paddedseat backs dcsigned Loss control Slowing down 5 impact loading would be bettcr thtn to yield untlcr Other cases of loss of control 4 voluntary seatbclt usage. It was rccolnmcnded that Driver's drowsiness 4 emcrgency exit windows hc required as well as an Dangerousovertaking 3 efiergencyexit door, Alcohol 2 feelingunwell 2 f)ue to the small number of severeca$e$ recorded in Driver Mechanicalfailure ' 2 to analyzecoach accidentsmust be each country, efforts lnattention I intensified,and the comparisonof independentstudies Unknown 1 must be encouraged. Moreover, in 13 out of 35 cases'the drivcrs were The Sample exceedingthe speedlimit for the type of road,

of Victims Characteristics Main Impact Typesand Distribution 'I ln two-thirdsof the cases,coaches sustained more than he study concerns48 accidcntsin which at leastone 'l'his shouldbe related to coach occupantwas killect.They includeall fatal coach one impact d uring the accident. Experimental SofetyVehicles

the fact that glancingblows are frequent.It is noticeable obstacle(which in l5 out of 20 casesis a rruck, and in rhe that the stoppingdistance ol'the coachafter the Ilrst othcrsa high, stitT,fixed obiect).Thc degreeof severityof impactis lessthan l0m in only two cases 'fhus, but ahove40rn injuriesaccording to thc extent ol' overlap in half thc cases. is given in lbr multiplcimpacts, thc main one Figure l. is taken to be that producingthe iatal injury. Three typescan be distinguished: Less Than l/3 Overlap Impacts r Frontal impacts:42 pcrcent(20/4g) r Rollover or tipping-over accidents:33 nercent They represent half of all fatal frontal impacts" (16/48) Respectively,44 percentand 48 percentare killed and r Orher cases:25 percenr(l2l4g) (includingfire, severely in.juredin this collisiontype. Seven out ol.thc I0 falling into watcr or a ravine,side impacts) casesare ofl.setto the leli (Figure 2). In accidentsin which at lcastone coachoccupirnt is killed, the distributionol'iniury severityamong victims I I 3 ro 3I 4 OverlapImpacts (Table2) in frontal impactsand in rolloverand tipping_ '['hese represent4l percentof killed and over accidentsis somewhatcomparablc. 22 perccntof severelyinjured. They occur mainly in slowing_down T'hchigh proportionof thosekillecl in theimpact type "Othcrs" situations.Due to the driver'sreaction, the right front is classiiiedas is duc to the:inclusion of the 4g concernedin 3 out of the 5 cases.

Table 2. Distributiorr of victims by impact type

lmpactTypes

Frontal Overturning Others Total Accidents . Falls Falls Fire intoa Side into Miscel- ravine impact$water laneous (numberof case) (ZOl (16) (1) (2) (41 (2t (3) (48) Kitted g0 46 48 25 11 73170 Severely Injury Injured l3S l 04 0 12 25 10277 Severity Slighrly Injured ZS0 262 O 13 30 1? 35 642 Uninjured ZSB 16l 16 o38 3 88 55S Total iZ4 EE7 64 50 104 23 126 1,648

persons burnedto deathin a singlefire accident,as well as accidents in which the coach t'ell into a ravine or into OVERLAP water (32 killcd out of 73 involved). It will beobscrved that cven in a sampleof accidentsin 119-3t4 which a coachoccupant was killcd, approximatelythree- <1/3 d ist rlbuted quartersol'those involved wcr.c uninjurcd or only slightly inj ured. .N- N ffi l_ry1 t4s r#l Frontal Impacts II TI II II II Iil The 20frontal collisionsresulted in 46 fatalitics(about ( numberof cases (10) (6) one-quarter (4) ol thc total) and I 35 seriouslyinj ured (half of thc total of seriously injured) out of 724 passengers killed 20 involvcd. 19 7 serlous,lyiniured 65 30 40 nront End DamageArea and Severityof Victims total 454 177 93

Frontal impactshave been broken down accordinsto Figuro l Distribution of injury the dcgreeof overlap of the coachfront severity of victims by with the strick overlap in frontal impactg

906 Section4. TechnicalJessrons

sl'l:!t -dl. I

Figure 2. 1/4 offset impact againet a truck-8 killed, 2 seriouslyinjured for 27 involved Figure4. Distributedfront impact against a truck-1 killed, 24 seriouslyinjured for 51 involvod

OVES!AP I V:r A 1Vt h;ir: mox tmum I Ve -3/+ intruriqn I (in m) distributad I I

Figure3. 1 / 2 offsot impact againstthe r€arol a truck- 1 killed,1O seriously injured for 28 involvsd

ir l rlr AI ll Distributed Frontal Impacts

Only 4 out of 20fatal frontal impacts showdeformations spread acrossthe whole oi the I'ront of the coaches involvcd.They resultin few killed(15 percent).hut the Figure 5. Number of killsd in the coach seriouslyinjulcd are rclativelynurlcrous (-i0percent). All in all. in Iatal frontal impacts,olfset cases cause 82 Rollover and Tipping-OverAccidents percentof'all deathsand 59 percentof seliousinjurics. Intrusion and projectienare' respectively,the main In l4 out of l6 cases.rollovers occurred after the coach mcchanisrnsof iniurics fol thosc killed (9 I perccnt)and had left the road besidewhich wasa shallowembankment for the seriouslyinjured (61 percent),I'hc two fatalities of at leastlm in depth.An initialimpact against a heavy b1,pro.jection took placein particularcircumstanccs (one vehicleand lossof control on a rnotorwaywithout the child standingup irt the gangwayand an elderlyper$on vchicleleaving thc load wcrc the two rcnrainingevents involvedin a rriultiplcfrontal impact accidcnt). precipitatingrollovers. Estimation of thevehicle speed at Among frontal projection victims, the body areasof the first moment of lossof control is givcnin l0 carsesby faceand kneellegare injured in 36and 30 percentofthe the tachygraphand 6 try the driver or witnesses(Figure cases,respcctively. 8). Expeimental Safety Vehicles

E r:i:- tr{:-f {:* a tochygroph [::i:i iit[rr-l-s-tg-1+11,J8 [: -1-.]r -r -- - -rr-. -.a' Y driver or witnesses

[':ld;i-] [: i -':,,*is. EH l''Ji! l-,ii ii ih

Figure 6.

r intrusion E eiect ion N p roiec t ion

olo stoppingdistqnce (in meterslfrom the 5 point ot which lossof conlrollook ploce- Figure 8. Estimatedinitial speedand stopping distance 4 of coachesinvolved in rollovers

The forward motion of coachesduring the accidcntis obvious. ln aborrt hall thc cases(7 out of l6), initial speeclswere 80kmih or more with distancesnceded to stop not lessthan 100m. Rolls (180oor more)with at leastonc contact"roof- ground" occurredin l0 cases,making l8 killedand 66 'l''ipping-over severelyinjurcd among the 329 involved, accidcnts(90o only) wereohserved in 6 cases--l2 killcd and 38 seriouslyinjured wcre recordedamong thc 228 involved in suchconfigurations. Thus, the importanceof tipping-overaccidents rnrrst not be underestimated.While 4 thercis no collapseofthc bodyin tipping-overaccidcnts, it must be mentioncd that, in fatal coach accidents, distributionsof the severityof injuriesare rather similar 35 between those involved in rollover and tipping-over accidents.

Coach Body Deformation and Severity for Occupants

The collapseof coachbody wasnil in 9 cases,partial in k i lled iously 3 cases(the crush did not exceedthc upper quarter ofthe ser side window), and substantialin 4 cases(the cant rail inju red reachedthe top of the seats). (46) Thc 7 caseswith collapseof the body superstructure (135) havebeen divided accolding to whetherthe tippingover or the rollover occurredon a tlat surfaceor againstan aggressivelocalized obstacle (an embankment or a Figure 7. Injury mechanismsin frontal impacts highwayguardrail- Figure9).

908 Section 4. Technical,Sessroas

intrusionand / or I part ial eiection fl total eject ion N proiection

Figure 9. Localised coach body deformation after tipping over on a motorway againsta median highway guardrail-5 killed, 14 seriously ,njur6d among 46 involved ,

It will bc ohservedin Table 3 that theside collapse after a rolloveron a flatsurface occurred in only 3 out ofthe l6 overturnedfatal coachaccidents, t'epresenting | 9 pcrcent of all seriouslyinjured persons. While coach deformatiotrs are spectacularin such cirses.this configuration is not representativcol thc majorityol seriouslyiniured persons in coach-overturningaccidents. It is noticeablethat 22 out ofthe 26 killed (exactplace unknown for 3, and I standingup in thegangway) were sittingalongside the side windows (Figurc ll). I'artialc' jection occurred in rolloversinducing a collapse of one sideol the coachbody structure.On the impact side,the cant rail and also the luggageracks are crushcd toward the gangwayarea (Figure l2). It isnoticeable that nonekilled and only a fewseriously injurcd were observedin the rows offsidethe impact in spiteof the reduction,there also, of thepassenger space. In thisconfiguration, all killedand mostof theseriously injuredwere sittirrg irlongside the windows Qn thc llnpact sicle.ln thc collapse,people arc partiallyejcr:ted through broken tetnptred window glassand crushedhetween the seriously kiiled groundand the exteriorof the coach. injured Thesevictinls represent 45 percentof thosekilled and 30 percentof seriouslyiniured persons. (30) (104) Last, the nonejectcdoccupants have sustained serious iniuriesdue to their projectionagainst upper interior Figure 10. fittings or the sidc part ol'seatlrames.

Table 3. Distribution of victiine by type of body deformation in coach-overturningeccidents

Rollover(Rl or BodY Obstacle Tipping-over(T) Killed Seriously All Deformation Su rface Accidents lnjured Involved

Nil or slight Flar 4(Rl + 5(Tl 11 47 288 Side collapse Flat 3(R) I 16 121 Narrow Local collapse and Stiff 3(R)+ 1(T) 10 41 148

Total 10(R)+6(T) 30 104 557

909 Experimental Safety Vehicles

Figure11. Distribution of 26 killed involved in ovefturn- ing accidents by seat location

Figure13. Fireaccident-48 killedout of 64 involved

fuel tank damagewith leakageI'or. three of them. A fire immediatcly broke out, especiallyinvolving the front of the coach,which was only slightlydarnaged by actual impac-l. Only l-5out o1'thc59 chilclren ancl I of the5 adultswere able to escapeby thc rear door during a period rrot exceeding 2rnin. All of thcm were uninjured. 1.he invcstigationshowed that thc victims were probablv asphyxiatedheforc being burncd. Falls into water wereobservccl in 2 cases,gencrating 7 fatalities by drownirrg out of the 23 involved in the 2 slightlydamaged coaches. It irppearsIrrlrn the survivors'statementsthat the main difficultyis to find and reachcoach exits quickly. As lirr as lirc accidentsare conccrned,it must be pointedout that the problem of emcrgencyexits must not be under_ estimatedsince one-thir.d ol all fhtalities(55/ 170) in the stuclicdsanrplc were rclated to this importantpoint. Only ialls into ravines more than 30m dcep are considered.As exccpted,the scvcrity is highsincc hall.of the involvecl(25 out of -50)were killed in thc 2 recorded cases.l-he analysispointcd out that l6 thtalitieshave Figure 12, Example .ll of side roof collapse_3 killed, heencrushed by the inrportantcolllrpse of thc front end seriously injured for 42 involved and rool structures.For thc remaining9 dcaths,the absenceof darnagein thcir Other AccidentTypes seat compartntentareas indicatedthat pro.iectionsof occupantswere too severe and exceedccithe trumirntolcrance limits. The l2 remainingaccidents generated 55 percent(94 As far asside impacts are corlcerncd, thc obstaclewas a out of 170)of all killcdbut only l4 perccnt(-Tg out of 277) truck in 3 casesand a tree in another. passivesafety in of irll scriouslyinlured studied in the sample. suchcollisions is not currentlyfeasible. For cxample,in The wide scattcrol' accidenttypcs (lirc. falls into a onetruck-to-coach accidcnt, thc truck drivcr lost control ravinc,side impacts, falls into watcr)and rcspective their on a bend and inrpactedthe middle side of a coach severityhas becnpreviously given (see Table 2). corning from the other way. I)espitethc smalldegree ol. Thc coachfirc prohlcrnwas dramntically highlightcd residualcrush (< l40mm),thc 6 personssitting alongside by the motorwayaccidcnt that occurreclat night in.luly thc windowsin thc impactarca wcre killed. I982 in Beaunc(Figure l3). 'l .lOtherr* he rcmirining3 fatal accidentsclassifiecl as Thc coachwas running at about l00knr/h and,due to weredue to thc deathof thedriver (driver leeling unwcll thc slowing dowrr of the precedirrgvchicles and clespite two times,and hit by an cxternalpro jectilc lost by a tr.uck brakinghy thecoach, it hit thc rearof tour carscausins in another).

910 Section4. Technical 'Sessiotts

Injury Mechanisms Discussion

can safetyof passcngercoaches be improved? Many differcnt kinds of injury mechanismsleading to How the answer could be by action on active safety, death were observed(Figure l4)- One primarilyon braking,and by actionin thefield of passive The importanceof fireTasphyxia' intrusion' and pro- strcngth,seat design, and bettelprotectron jection againstthe occupantcompartment walls will be safcty-body againstthe consequencesol fire. especiallynoted, These three mechanisms together account herefor virtually all thecascs of deathtrnd serious injury' Braking ImProvements

phyx at the instant of impact trF a s i a-fire The kinetic energyreduction can be clcterminanton the accidcnt'sscriousness' It is intrusion thus necessitryto use to the ntaximutnthc potcntial I possibilitiesol' improvenents in braking performatrce' - eiection l heseirnprovemerlts should include ff r Improvementsof spccdreduction performancc brake ovcrhcating,cspecially in long proiection without W descents r Rcductiontrf minimum stoppingdistances when other the normal hrakesare used ffi (drowning,externol r Maintettanceof directional stability during roiectile.etc-) braking olo It must be remembercdthat in l2 out of the 4tl cases studiedit wasconsidered that betterbraking performance would haveavoidecl the collision,or, at least,redr'rced the collision sevcrlt)'. Mandatory retardersare recommendedas a counter- measurein one ca$e,but, as it is well known. most coachestoday are not equippedwith sucha device' Stoppingd istancered uction is concerned in 7 cases'A shorterstopping distance cannot always avoid thc col- lision. but it permits a reduction in its seriousness' providcd,of c()urse,that thedriver is not temptedto drive at constantrisk. Thr.rs.the minimum stopping distanceusing normal brakcscoulcl be reducecJby l2 to l5 percentand should not tend to increasethc risk of wheel-locking' The fitting of an antilock braking systemwould have ol'the48 cascs in our study(loss of beenfavorable in 4 out 'the control during braking on slippery surfaces)' advantagcis increasedfor vehicleswith powerfulbrakes reachingwhcel-locking limits evenon dry asphalt' 'l hus,these two measures-'minimum stopping d istance - $ of braking and fitting of an antilock braking dcvice 3 shouldbe appliedsimultancously' il PassiveSafetY

passivesafety of coachesbe improved'? k illed serlously How can the Inlureo To answcrthis question, thc injury mechanismsleading ( to dcathand seriousinjury mustbe borne in mind(Tahle e4) (38) 4). lntrusion is the leadingcause of fatalitiesin coaches' In Figure 14. Injury mechanisms in accidents classified as "others" frontal impacts, it would be tJesirableto incrcasefront

911 E xp erim ental Sa,fety Vehicle s

Table4. Sumrnaryof injury mechanisms few cases of deaths due to projection that occurredmainly in f rrllsinto Seriously a ravine Thc Killed injured countcr.lrleasurcof universalwearing of (n -- 17Ol (n = Z77l 3-point beltsirmong all the seriousll,in jured in our samplewould, accor.dingto our estimate, Intrusion 47% TEo/o have lessenedthe injuriesof.43 percent ( lZ0 277) Asphyxia-Fire ZBo/o O% l of such nonfatally injured peoplc, Totalejection 12% 1E% taking ali inrpacttypes .l-his Projection l% iO% togethcr. perL-enragec()ntains Other E% OTo a wide rangc of conditions of vcry dil.fbrent presumedeffectivcness and type of protection 100% 100vo achicved('Iable -5). I he countermeasure of universalwearing of a lapbelt arnong those scriously injurcd structure resistance.-especiallyin highly in .rur offset impacts, samplcwould but the I'casibility haveforcstalled 25 perccnt (701277) of this is doLrbtful.Rcinforccd coach of suchinjuries, taking all impact stiffnessair.ed at avoidingintrusion typestogether. frornthe Iront row The dilfcrence in the prececlingestrmates is due of seatscould be an ob.jective.The problcnr of prorecting to the fact the wearing of a lapbelt thcdriverand thc occupantofthe hostess would not seatremains. In provide a cranio-cervical tipping-overand rollovcracciclcnts, protcction in trontal proposer:lstandarcls( I) irnpacts. aimed This evaluation does not take into at avoidingcrushing ofthe superstrucrurcconcern accountthe possibleadverse e ffect mentioned only a rnirxirlum ol 6 to l-5pcrcent of bv all severelyinjured recentreports(3) victims in Irontal cases. in thesample. In thelight of our analysis,ii may I{owever, these are estirrrates be fearedthat, even if onc managecl of maximum to climrnatesuper- benefits,and structurecollapse it is believedsuch clevices woulcl be sufiiciently,the numberof seriously .fhus. jured lessthan universallyused in coaches. in victimswould not berccluced signilicantly the b$cause only cfficient action, of the high risk of c'jcctron, without compulsion for coirchusers, consists of improvirrg Ejectionis the causeof lZ of l5 perccnt the restraint of serious ef'lbctof seat backs. injuries and occurs mainly in ovcrturning accidents. r Seat-back Ejection lmprovements_Thcsemodifications occurs via side windou,s (7 I percent), the would aim at achievingthe following oh.jectives, wlndscrccn(22 pcrcent), and l.herear window (7 percent), espcciallyin frontal impacts: A simplc lapbelt would provide efl.cctiveprotection l_irniting the forward movement againstthe risksrclated to total of the ejection.A 100percent occupant wearingratc to the back seat wjthout over_ woulcleliminatc l2 percentof all cleathsand 'l loading to the occr.rpantseaterJ many serior.rsinjurics also. o combat in Lront of e_jcction.the other r him. alternativcis that of restraining uncontiolledkinematics Rcducing by thc the seriousnessof lower limb windowsthemselvcs (ae:tingasa net). This coulcl be lmpircrs(for examplc, knee achicvedby addingglued laminated ,1.his by bolsters)and glass. totally ol passil,e cranio_lhcialinjuries (for examplc, by safety charactcristiccoulcl in addition improvl coacrh appropriate padding). Such modifications strucluralresistance. Suc:h an 4pproacl.r,hoycvcr, shoulcltake into acL,ountthc simultaneous hasthe disadvantage of militatingagainst rapid passenger necd to protect both childrenand adults. evacuation(except, if satisfactorysolutions in termsof especitrlllrthg clderlv. emergencyexits. whatever the coach,sfinal position Comparcdto -j-point atter irnpact can be rJevcloped). beit_wearing,the elTcctive_ ncss of this purely passiveprotective devicc is I-ast,it rteemsthat loweringthc heightof the bottom of lesspronounced bccause the sidewindows incrcases cjection it only concernsoccu_ risk. tn theabscnce of pants eithcr scated hehind a seat back; and such maki'g the window act as a net or of a restraint device cannot, in case system use,the bottomof the of very oblique frontal siclewindow shoulcl not be lmpactsr prevent all risks lor occupantsseated lower than the shoulderof an averagcadult passengcr. near the centralgangway. Frojectionof'a passenger against iirtcrnal panelsofthe All in coach compartment all, this countermeasurecould, in our was the causc of half: thc serious view,sliminatc 20 percent of injurics,but only of 7 percentof deaths. all thosescrrously It is only really injured. possiblcto envisage two founfernreasur.es, that is wcaring a restriunt The last point related to passive systcrnor rnodificationsto scat safetyis the conse- backs: quences of firc. l.ire . RcstraintSystem_Case_[y_c45g as a cause of dcath is rarc, analysisshows Neverthcless, that wc shouldrnention that theIire casestuclicd wearing a seatbclt,evcn a 3-point type, highlightsthc problem ofheing able woulcJnot havcavoidcrJ with certainty to get occupants any of the clcar ol coachesquickly. The same *oui.l b* true lor 912 Section 4. Te c hnic al .lesslorzs

Table 5. Presumed effectiveness of 3-point belte for all seriously, but not fatally, injured occuPants

Numberof seriouslyinjured Presumed lmpacttypes avoidedby preventionof 3-pointbelt effectiveness

.projection ..,ejection

Frontal 50 5 41%(55/135) Overtu rn ing 36 24 577o16o/1o41 Others 1 4 13o/o(5,i 381 coaches falling into water. Apart from such cases,the especiallyfor highly offset impacts,would be desirable, problemdoes not arise. but thc fcasibility ol this is questionable. One may note that the meansof achievingthe two aims In the sampleanalyzed, death by bcingthrowtr forward of reducing ejection and facilitating evacuation are against a seilt back has not been observed,but this currcntlycontradictory, Can the fiequency ol'ejection be accountedfor half of thoseaccidents involving serious reduccclby increasingthe number of emergencyexits. injurics.['articular attention should be givcn ttt improving especiallythrough the sidewindows'l $eatbacks to insurcadequate passive restraint lilr head In this context, doors seemto bc the emergencyexits and lou'erlimbs in frontal impacts. that arethe most rational and involv$the fewest problems. Total and partial ejectionarc frequentand severein In case of tipping-over accidents,the possibilitiesof rollovct and tipping-overaccidcnts. Window rctcntion transl'orming the rear window and roof windows into usingglass plastic products moutrtcd so as to actas a net emsrgencyexits cannot be rteglected.In all cases,the could prevent e'.icctionwithout any restraintusage. But rapidity of evacuationmust bc a priority, and everything sucha deviceis in conflict with the needto bc able to use must be done to maintain clearand frec gangways,door all glass-coveredapcrtures as potentialemergency cxits, irpproaches.and emergencyexits. particularlyin cascsof lallingillto wateror theoutbreak The effort ttt obtaitrbctter llammability characteristics of fire, lmprovetrictrtsin escaperr)utes lbr the last two of vehicleinte rior materialstlust bepursrrcd, but it isalso ca$esmust be considered. necessaryto considerthe effectsof smokeemission and In caseof i'ire,measures aimed at evacuatingsmoke toxic gas,which may accompanysuch fires. The Iact that emission will reduce risk of asphyxiaand increirsethe smoke is opaque is an important aauseof panic, and time availableto leirvethe vehiclc" carbon monoxide inducesparalysis, particularly ol the To provide a chanceof assessingmore preciselythe lowerlimbs. Measurcs aimed at improvingsmokc emission effectol'l'easible and necessarysal'ety measures. doing so evacuationwill reducethe risk of asphyxiaand Iacilitate on the basis of very severecoach accident data, the the rapid escapeof coachusers. comparisonof indcpendentstudics has to be intcnsified through the auspicesof intertrationalorganizations.

Conclusion Acknowledgments :

Travel by coach is by far the safestmeans of road The iruthorswish to thank the GendarmerieNationale travel, but seekingways to preventcoach irccidents or to for their ceopetation;without it, this studywould not lessenthcir el'fectsis still necessary. havcbeen possible. lhis survey,bascd on 48 fatal coachaccidents, shows it is clearly preferablethat accidcntsbe avoidcdby greater care being taken by coach drivers, since73 percentof References these were blarneworthy in the studied sample. But "Coach bccausean exceptionally large nutnber of peopleirre at l. Baxter, W.L., accidents*a pcrspective," risk in suchaccidents, improvcmcnts in theconstruction lnternationalCongress of FlSlTA, Hamburg,1980, o1'coachesmust also be dcveloped if someol'the causcs of VDI tlcrichteN. 367, 1980. "An death and seriousinjuries are to bs minimized. 2. Stansiler,R. L., and R.A. Romberg, analysisof Shorteningstopping distances by increasingbraking accidcntsinvolving buses and an assesstncrttol' the perfrlrmancescould avoid or reducein severityabout l5 needlbr saf'etybelt requircmentsin suchvchicles," percentof the cascsstudied. Proceedings22nd AAAM Conferenceand the lntrusion in frontal impactsis the main causeof death IAATM Vll Conference,Ann Arbor, Michigan, in coaches.Increasing coach front $tructureresistauce, Julv l0-14.l97tt.

913 Expertmental Saf"+ Vehicles

"School "Statistique 3. Farr, G.N. bus safetystudy," Crashworthi- 5. Gendarmerie Nationale, annuelle des nesssection of Transport(:AN,4D,4, 1985. accidentsde la circulationroutibre." Annee 1984. "A 4. Davis,M. M., studyof someschoolbus crashei," Froceedirrgs2lst AAAM Clonl'erence,Vancouver, British Columbia, Septemberl5-1"1, 1917.

Optimisation of n Bus Superstructurefrom the Rollover SafetyPoint of View

D. Kecman a residual(survival) space defined with referenceto the Faculty of Mechanical Engineering,Belgrade H-point and centrelineof the seats.Such a test is very Consultantto Cranfield Impact Centre expensiveand unsuitablefor developmentpurposes. The pendulumtest on structuralbays is carriedout by G.H. Tidbury an oblique impact at the cant rail level. The spcedof Cranfield Impact Centre, impact is 3 to 8ms,while the impact energyrepre$ents a Cranfield, United 'lhe Kingdom fraction of the total energy tbr the completebus. energyis proportional to the massof the vehicleand the verticalfall of the centreof gravitybetween the maxrmum Abstract levelof thetitting platfbrmand theposition corresponding to the first contact of the body with the ground. The Bus superstructure$ may soon be subiect to new energydeclared for eachpillar of the bay must meetfive rollover safcty requirernents.Increased rollover safety constraintsspccified by regulation. must beachieved with minimum weightor costpcnalty; The introduction of the calculationmethod was based hence,optimisatirtn has a significantpractical relcvance. mainly on the work carried out at the Cranfieldlmpact This paper dcmonstratcsthe possibilityof predicting Centre(l-6), although suchan option was in the original the collapsc performanceof a bus superstructureby a Hungarian submissionto the Working Party. It will completelythcoretical model. The work describedalso almost certainly be a reqrrirementthat thc calculation created a basis for the option offered by the new must includeeffects arising when the structure undergocs regulations that allows type approval by calculation large plastic deformations. Separatecomponent tests combinedwith somecomponent tc$ts. lt alsoshows how may be requiredto verify theassumptions for thecollapse a sal'etystructure can be optimiscd from the weight or bchaviourof components. cost point of view by nreans of a special computer A calculation method offers not only the chanceto pr()gram. obtain type approval without large-scaletesting, but it is alsosuitable for bus body developmentand optimisation Introduction in terms oi'both safetyand economy.

The importance of adequate bus rollover safety has Theoretical Prediction of the Collapse beenrecogrrised for many ycars.Bus superstructures may Behaviour of a CompleteBus soon be subject to new rollover safcty requirements, which arecurrently being discussed by Working Party2g Bus bodies under impact develop localisedbending of the ECE,. failures-hinges,which absorb most of theimpact energy. The regulationsare likely to offer the following choice lnvestigation of almost 30 bus rollover accidents(S) of methodsfor obtainingtype approval: identilleda varietyof collapsemodes (Figure l). Mode A r A standardfull-scale rollover test with hinges at the waist and cant rail levelswas most r Pendulumtests on individualstructural segments common. Hingesat thefloor level(B,C) occurredmainly (bays) near door apertures,while roof membersalso collapsed r A calculation method, combined with some (D,E) in somecases. Control of the overall collapsemode componentte$ting is very important becauseit affects the amount of The stanclardfull-scale test implies rolling a complete del'ormationprior to the intrusioninto thesurvival space. vehiclefrom a tilting platlirrm onto a horizontal plane Mode A usually provides the greatestangles of hinge 800mm bclow. The superstructuremust not intrude into rotation.

974 , Secdon4. Technical,Sessrozs

sheets.A quasi-staticanalysis ol.a standardrollovcr test situationis possiblebecausc of ir relatively low itnpact speed(less than l0ms) and becausethe mass of thc [ana,-ln[*7n the nrassthat is deforming structure is much lessthan A B c 0 E F being retarded. Collapseaualyses were performed using the Cranfield Figure 1. Colfapsemodaa of bus rings StructuralHigh Dclormation prograrn CRASH-l), u'hich allous Ior the highlynonlinear effccts ol largedeforma- tions, hinge occurrence,and variable hinge momcnt- Isolatedrings collapse in mode F, which demonstratslt rotation curves, the effect of the surroundingstructure (cladding, longi- 'l'he analysis started with the elastic finite element tudinal beams,seats, floor) in alteringthe collapsemode morJelin Figure3a, which included all themain bearr and of any ring in a bus body. Theseefl'ects werc studied plate clcments.l-oads were applied obliquely along the within theelastic range(6), and it wasdcmonstratecl they cant rail and the main load paths determined'It was can be modelled successfullyby springs C and C, shown theoretically(3)that thc collapsemode can be attachedas shown in Figure 2. Thc impact load P is controlledby carel'ulselection of the sidecomponent$ appliedobliquely to one of the cant rails. belou,thc rvaistrail, The modelfor collapscanalysis was Spring C hasan axiirl and bendingstiffness selected in much simpler(Figure 3b) and includedonly thoscmain sucha way that the bcndingmoments of the floor, waist, elementsthat would form thc rnaincollapse mechanism. and cantrail levelsof thesimplil'icd rrrodel correspond to Fictitious beamswere attached late rally to tlte pitlarsat those obtained by a much more dettriledelastic analysis of a segmentof the body. It wasalso dcmonstrated that ringswith an incomplete floor member (i.e.,without thc dotted line in Figurc 2) are muchmorc ilexible than thc complete ones. Howevcr, the typical restrainingeffect ol'the surroundingstructure in the verticaldirection (simulated by springC) is suf'ficient to eliminatethe effectoi'the central gap on thc collapse mode. A collapseanalysis of a completc,all-metal body of a 'l'he coachwas carried out(3,4,6). skelgtonwas made of rectangularand squaresectiorr tubes clad with aluminium

SimFl if ied Frame*Drk Structure for CRA5fl-DAnd I y! i s

c c 0!tput fron CRAsH-0Analys i 5 Shdcing oeforned Shdpd dnd Sequerrceof FormaLjoF of Plastic HinqeS,

C1 C1

ft7al 8 77'

Fiqure 3. computerModelS of Bus Stfutture. Figure2. Collapse modo of bus ring with springs simulating the connecting structure Figure 3. Computer model$ of bus structure Section4. TechnimlSessrons

the waist rail levelto simulatcthe effcct of thoseelements in thc sidestructure that wcreeliminatecl ll.om the first model. 'l'he theorcticalcollapse mode (Figure3c) predicted hinges at the cant rail and waist rail level in all rings exceptthe front door, wherethe hingcoccurrcd below the waist rail. Secondalyhingcs, which did not take part in the main collapsemcchanisrn, were also prcdicted at the floor level of all rings, The full-scalcrest ol the vehicle (pcrformedafter the analysis) gavc an exccllentagreement with the predictcd location and charactcr(primary or secondary)of all hinges. To predict the iinal deformationsof the structure,it wasnecesiliary to determinethc energicsabsorhcd by each Figure4. Theoreticalmodel of hinge ring and comparethe collapsemecha- sumwith thetotal energy input. At nism thc tirne of analysis.variable hinge monrent-rotatton curvescould be modellcd in two-dimensionalstr.uctures deformation, In sucha way,it wasalso possible to derive only. The theoreticalload-dcflection curves of all rings the theoreticalM-d curves(Figure 5c) in termsof the were,thcrcfore, produced by scparateanalyses. Rings A sectiondimcnsions a, b,t (Figurc5a) and the yield stress o and G (Figurc 3c) includedtwo norrnalrings, but they and maximum nominal flow stress of the material collapsedditferently. The elastic stiffness ol all ringswas (Figurc 5b). The thcory was verilicdby vcry extensive obtainedflom the modelin Figure3a. and thethsoretical experinrental work on tubeswith a/ t ratiosbetween 9 and collapse phase was common to all normal rings. 128and a/b ratiosbetween 0.33 and 3. The agreemt:nr J'heoreticalmoment-rotatiorr curves, including the calcu- with experimental data was excellcnt (examplesare lated stririn-r'atrretlect, were uscdin the moclel. shownin Figure6). 'l-he Thc energyinput per ring was cquatedto the arca thcory provided a basisfor the developmentof a undcr the load-deflectiondiagranr, and henccthe maxi sectionoptimisation program WEST(B) for thcselection mum ring dcf'lcctionswere calculated.C omparative of thc lightest or cheapcststandard or nonstandard resultsal'c sumrnariscd in TahleI, whcr.ed,,,reprcsents the section tubes meeting the ftlllowing safety criteria: maximurl dcflectionof the cant rail whenit is irnpac-tecl maxirnum bcnding str.ength,energy absorbcd, and along a line at 3()' to thc floor cr.oss-mernher.The remainingstfcngth altcr a givcnhinge rotation angle. lt dif'lercnccis lessthan l5 pcr.centexccpt in ring F (21 pcrccnt),to which displacementscoulcl not he 'l applicd clirectly. hc agreemcntis, in lirct,bette r than is 'l shownin able I becauscexperimentirl displaccrncnts wcre mcasuredafter thc testwhcn somespringback from thc maximurndellections hird already taken placc.

Section Optimisation From the Safety

Point of View 6o (H/nn? 66 The bending moment that can be carried by a thin, F walledrectirngular section tube drops off rrrpidlyafter the onset of collapsc.I{epeatability of collapsemodcs pro- duced hy uniaxial bcndingcnabled a del'initionol the thcoreticalhingc collapscmechanism to be madc(6.7). The bending and rolling dcformation along the con- centratedyield lines(Figure 4) was relateclto the hinge Figure 5. Input parametersfor calculation of theoreti- rotation angle d, as was the energyabsorbed by plastic cal hingo momBnt-rotationcurves Table1.

Rrng ABCDEFG d-(theoreticalXmm) 536 555 505 491 488 488 430 d-(experimental)(mm) 577 550 508 466 424 402 385 Section 4. Teehnical.Se.tsiozs

0 l0 ?0 l0 cl%l

Figure 6. Theoretical(solidl and experimental(dottedl curves for a rango of tube dimensions alsoenables selection of minimummaterial properties if The mostgeneralcase corresponds to theselection of a sectiondimensions and the target sat'ety performance are minimum wcight theoreticalsection made of a given specificd.The program can also producethc bending materialand nreetingonc, two, or all threeof the salety collapseproperties ol'given sections, which may be used constraints.By specifyingthe ratio of the properties further,eithcr directly in designor asinput data to finite about thc two principalaxes, it is possibleto determine elcmentprograms for collapscanalysis. theaspect ratio a/ b of thesection and reduce the number of variablesto two, saya and t (Figure5). Eachof the constraintscan then bc solvedfor the wall thicknesst starting I'rorna lange ol valuesof thc width a. l-hree l{mrr,} curvcsare thus obtained(1, ll, and III in Figure7)" The with minimumarea, i,c,, weight, corresponds to 25 section the point A that islowest on thecomplcx suriace defincd by constantarea curves (shown solid in Figure7) but that ?0 doesnot fall belowany oi'thc threecurves I, II, and III.

l" Procedure for Optimisation of a Bus

i00 mm StructureFrom theRollover Safety Point l0 of View 200 05 15C l0f Optimisation of a bus structure from the rollover 50 safetypoint ol viewis pcrformed in thc lollowingstages: 00 (a) Choiceof thc generalconcept (e'g., two sal'ety ?0 l0 {4 50 60 70 o(mm) ringsat the lront and back,or no specialrings). Subsequentstcps allow a parallelestimate of Figure 7. Diagram illustrating operation of optimisation program WEST both options.

917 Ex p eriment al Sa_fe ry Ve h ic les

(b) Assumestarting section dimensions and perform The time involved in carrying out the procedure an is short elasticanalysis of the completehocly or the cnough to becomcpart ol'theearly design process l.or a scgrnentas if it werc going to be subjectto a ncw vehicle. It provides the most rational and cost_ pcndulumtcst (main load pathsare detcrrnined cft'ectivemcthod for the designol'structurcs to comply and inforrnationon the etl'ectsof noncollapsing with the ncw strengthof superstructureregulatirtn. membcrsis estirnated). (c) Pcrforrncollapse arralysis of a simplifiedmodel, usingcollapsc propcr.ties calculateci bv the nro_ Acknowledgments gram WEST and allowingfor thc futi rangcof While delbrmationsrcquired to absorb the energy the optimisationcode is solelythe work of thc first requirecl. author, thc generalmethod of analysingthe whole (d) structure Annlyse the resultsof stepc and cleternrinethe was dcvclopedat the Cranfield Impact Centre under the hingc rotation anglesand energiesr.cquirerl. [Jse sponsorshipof thc Departrnentof TransDort. theseas input data to rhe prograrnWEST to deterrninenew scctionclimensions or matcrial References propcrtres,dcpencling on which of thc four programoptions is consideredrlost .,Analysis significant l. Kecman, D,, of framework_type (lighteststandard safety or nonstanclar.dtube, cheapest structures " in road vehicles, .ttru( tural (lr as hut o r t hi_ standardscction, or. material for givcn dimen_ nrss, edited by N. -Ionesand J'. Wierzbicki. sro ns). Ilutter_ worths, 198-1. (e) Repeatstcps (c) anct (d) until thebest solution is 2. M iles,.f . C., .-t'he determination found. of collapseload and encrgy absorbingproperties of thin walled beam (0 Repeatsteps (b) to (d) to checkthat thealterations structur.esusrng rnatrix methods of analysis,,,1nt, do not introduceimportant ncw efl'ectson load Journal of' Mechunit:al St:iente,lg. 1976. redistribution,elastic stiflness. ctc. 3. Wardill, G.A., antJD. Kecman,,.Thcoretical (g) predic_ Design and producecornponclrts (beams and tion of the ovsrall collapsemode and maxlmum .loints)based on thethcoretical analysi.s and test litrengthoI a bus structurein a roll over situation,,, themto collapsestatically irncl dynamically (by a ClongrcssFISITA, Hamburg,19g0. srlall pendulum).This exerciscshoukl prove 4. Kccntan,L)., and G.H. Tidbury, .-Theoreticalpredic_ that theassumptions corrcerning bearl and joint tions of thc completecollapsc behaviour of a coach stitfness,strength, and energy_absorbing propcr- subject to the proposeclstandard ttesare corl.ect. roll over test,,, CongressFlSlTn, Melbourne, (h) Accept 19g2. tlresolution, or repeatthesame procedure 5. Stluctural DesignGroup (Cranfiel

918 I Section1, TechnicalSessrozs Improvementsfor Bus Safety

Klaus Rompe and Hans Joachim Kriiger Institute for Traffic Safety, TUV Rheinland e.V..Cologne

Abstract

Today about l4 percentof passengertransport on the roads is accountedI'or by buses.For bus occupants,the risk of beingkillcd asa resultof a buscollision is about 40 times lower than in passengercar accidents'Therefore, busescan be classifiedas road vehicleswith the most upgraded safety.Nonetheless there are someaspects of safetystill to be developedin the futurc: r There is still a lack of objectivecriteria designed to assessthe driving behaviorof the new type generationof high-capacitybuses. Underfloor cockpitsrestrict the driver'sfield of vision and exposethe driver and, hence,the occupantsto additionalrisk of injury in accidents. Busdriver cockpits could be adequately improved at Iow cost. The anchorage of $eatsand the capacity of deformationenergy of backrestscan be exploited to incorporatean advancedpassenger restraint system. There is needfor specifyingcriteria of effective- nessapplicable to emergencyexit systems. Figure1. Modarn high-capacity coach dimensiona (above-18 x 2'5 x 4m' seatsl(xl'144;below- 18 x 2.5 x 3.2m, seats 68-80) Safety of Buses articulated form-have becomemore popular, Today approximately l4 percentof thetotal passenger and, asa resultof theirincreasing number, they . transport on thc roads of the Federal Republic of alsoplay a rolein theoverall accident occurrence. Germanyis accountedfor by buses(l).It is obviousthe There is. however,especinlly for thesevehicle the safetyof thescvehicles is a reasonfor thcir attractiveness. types,very little knowlcdge concerning driving The risk of beinginjured in an accidentby busis l0 times properties.particularly in criticaldriving situa- lower than in a passengercar accident.Referring to the tions(2). more numbcrof kilomctersper person, the riskof beingkilled Recentty,for reasonsof cost, more and construction. is even40 timeslower. There arc, howcve r, threeessential lorry chassisparts arc usedfor bus will arguments Ior a further increa$eof bus safety in the This raisesthc questionas to whetherthis in a future: changethe design strength ofthe bodywork L Along with the technicaldevelopment of safety collision and the stt'ucturtilaggressivity ol' the componcrrt$in buses,e.g., anti$kid devic-esn vehicletoward other vehicles. retarders,headlight range adjustment, and pas- 2. Due to the heightencdseating position of bus sengerprotection devices, there has also beena occupants,the consequencesof collisionswith change in the construction concept of buses,lrr othertraffic participantsarc gcnerally nQt severe. modernbus construction, the permissiblc Iimiting The constrtrctionof high- and douhlc-decker valuesfor the outerdimensions--l8m long, 4m buses.however, could lirvor the frcquency ofthe "running high, 2 5m wide,and weightZtlt-today arefully accidenttypc offthe road'"l-hcdanger exploitecl(Figure l). F-orlong-distance travel, ariscsol overturningirnd, at thesalnc time' up to high- and double-decker buses- even in an 150 passcngersat'c sub.lectedto a hazardous

919 Experimental Sof"ty Vehiales l

situation, e.g., individual survival spaceis not grantedby the structuralstrength. 3. Children and eklerlypersons ligure significantty in the numher of injured bus passengers(3), , Sincc thesepersons are morc or lessclepcndent on bus transport,their protectionshould be partrcularlyconsidered. By order of the Fedcral Ministry of Transport,the Institute Ior Traffic Safery of TLiV Rhcinlanrj has conductcdseveral invcstigations to finclncw possitrilities t() impl'ovebus sal'cty. Figure 3. Eye level in underfloor cockpits Saf'etyis hascd on the ergonomic design of the bus driver'sworkplace. The driver obtainscssential irrlirrma_ tion I'or driving by his vision. Thercfore,the sight from thevehicle to thefront, to theside, and via themirrors to the rear is ol'particular importance(Figure 2).

ire"i 14 m ;'

Figure4. All-roundfietd of vision Figure 2, E-point feveland frontal direct field of vision

Also, control switchesand For high-decker monitoring instruments buscs,an averageheight ofthe driver,s must be arrangedfavorably within the driver'sficld of eyesof 2.2m above the roatl was calculatcd.Togethcr vision.It is,howevcr, questionable whcther he is ableto with the extremely large surfaceof the windscreen. this observeup to 84displays besides his actual task nreansperfcct vision to ofdriving thefront. For underfloorcockpits, (Figure5). corningmore and nroreinto ().5m userthc eyelevel lower Bascd on our measurements than .l.he and driver interviewS, usual causesproblems concerning safety. all_ further improvements are requircd, especiallyfor the round visionof thedriver is limited, and the danger of the ergonomic dcsign of control devices at the driver being injured in an driver,s accidcntwirh a pzrssengercar workplace(SJ.One example (the is a suitableresting place for most Ircquent participant in a collision) is in- the left foot in a restposition.'l'he slopc of theaccelerator creased(Figurc 3). frequently does not meet comfort requirements.To lf the sight conditionsto the right and to tne rear are reduce the timc of changefrom taken into the acceleratorto the consideration,problems are causedby the brake pedal, the half-loaded accelerator should be conllict between structural strength and the required positioned approximately to the sarrreheight unhinderetjall-round (Figurc as the vision a)(a).Nonmisting, unopcratcdbrake pedal. heatedsidc windows, additional nrirrors. and a television Within the driver'sreach, all control devicesshould be systcm at the rear of the vehicle could be technical arranged within a radius of approximately 700mm solutions. A comparative assessmentof the different around the shoulderjoints. This requiremcntis not yet possiblesystems is beingelTected at frresent. fulfilled in all cases.The movementsof the gear level,

920 Section4. Technical Se,eslons

-- 4G

Figure 5. lnstrument pan€l with 84 controls and dis- Figure 7. Interruption of two-handed steering P16Ys switchingon the wiper/washersystem which arestill necessary,exceed this rangeby lar (Figure Although the driver's workplaceconditions in buses 6). arc sul'ficientin general,these example s showthat furthcr The example given in Figure 7 shtlwsthat one hand improvementsare possible without Ercateltort. must leavcthe steeringwheel to activatethe windscreen Fifty to 60 perccntof all bus accidcntsare head-on wiper. 1'o maintain continuoustwo-handed stccring, irll collisions,more than hall'ol which are collisionswith controls operatcdf requently should be locatedwithin passengercat's. Because the pa$scngerseats are locttcd fingcl rcach around thc sttcling wl-reel. about l.2m abovethe road, the risk of bus occupill'lts bcing injured is relativell'low. However,the risk is r*' y 'fhe considcrablyhigher in overturningvehicles. risk of i*; thc occupantsbeing injured or killcdoccurs particularly whenthc vchicledeformatiotl d()cs not maintainneccssary ****- survivalroom for thc passengerseats. If the passcngers are thrown out of thc vehicle,the risk of bcingkilled is about six times higher than in similar accidentswith passengcrcars(6,7). In about50 percent ofall ovcrturning -l-herefore. accidents,passengers arc throrl'n out. the "overtulning ffi accidenttype of vehicle"must bc given more attcntion in the future. In the Federal Repuhlic of Germany, long-distance buseswith a permissiblctravelling speed of I00km; tr for #i motorways rnust he equippedwith lapbcltsfor those G seatingpositions that do trothave a similarseat in front of them--the so-calledrisk scats. However, the systcms availableat prcscntwith uncomfortablelocks, long belt straps,4sfl cvcn with autotrraticlocking retractorsare not acceptedvoluntarily by the passengers(Figure 8). Moreover,automatically locking lapbelts, such as those currentlyin use,restrict the occupantsand it hasproven difficult to havethem fastenthcir belts.lt has,thclcfore, been investigated in comprehensivestudics how to improvc the restraininge ffect of seatsystcms to add to occupants'safcty(8,9). During thc first stageof the investigation,we varied the distirncehctween the seatrows I rom 700to l ,000rlrrI.In simulatedhead-on collisions with vehicledccelerations of 59, we measuredthe strainof diflerentsize durnmies in [ldnmi***lwd*'.s*,r,"istrlllr*+*h+ sledtests. Figure 9 illustratesthe tnovementpaths of an Flgura E. Nonergonomicgear level position adult dummy for head,chest, and pelvis.On thc leli part Ex p ertment al Safety Vehlcles

Subsequently,we carried out fu(her impact simulations with a vehicledecelcration ol l0g with theoptimum seat dist:rnceto investigatethe straincrn the dummies and the delormation bchavior of thc front backrests.primarily wc statedthat theseat anchoragc did not standthe strain and looscned.Figure I I showsa constructiontlrawing of thisanchrllage on thelelt outerwall of thevehiclc and on thc bottorn of the right sideof the vehicle.To chansethe

Figure 8. Lapbelts on exposed seating positions in 100km/h limit coaches W

Figure1'1 . Lateraland insideelements of seat anchor- age Figure 9. Trajectoriesof child_dummymovements at Sg decelerationin different distances between number of seat rows easily,the anchorageis executed two forward_faced double seats {left_70mm; relativelysimply. Partially, only compression joints right 900mm) have beenused (Figure l2) lf the I'rontseat brcaks loosc, the impact strain on thc occupantsis relativclysmall. If, of the figure,the distancebetween the seatsis 700mm:on however,several scat rows lousen,the occupantson the thc right, it is 900rnrn. l'he test resultsshowecl that, I'or front rows are subjcctedto considerablestrain. Further- child as well as adult dummics,a minirnurnof injurics more,partially looscnedor displacedseats will hinderthe may occur with a distancebetween tlte scat$ g00 of an

922 Section4. Technical,Sessfoas

;fi*r

I i$rl r ilHlf;it p,"

f; h fl

Figure 12, Failure of anchorage elemente in a simulatad 109 frontat impact

single and developa simplifiedtest procedurc. In severalstagss, emergcncyevacuation systcm. After a collision. In the rcquiredtnitsscs were reducedaccordingly witl'rout exits may be blocked within the collision range' in the considcrablychanging at thesarnc time the kinctical and gencral,thele aresufficient cr"acuation possibilities kinematicalratios during thc impact(Figure I J).Such a resitlualcompartmettt. than testprocedurc will givetrluch hclp to the tnanutacturers ln caseol'the vehiclc overturning, however, morc of bus $eatscorlcerning inclcascd sal'ety for passenger hall the exits may be blocked. Escapingfrom the physical roorri. If the resistanr-:eol' the seat atlchorageon lhe compartment to the tttp requirescnormous ctionto the vehiclebottorn is guaranteed,it will dcline individual strength.Clompared to thc normalescape dire a detour' survivalroom for eachpassenger, considering also the back or throughthc roof, thisway $eemsto bc clr)L:rgency requiredbackrest deforrnation (Figurc l4), l-he rnost intportant requiremcnt lbr an At lcast lttr two ac:cidenttypcs. the severityof the evacuationsy$tem is caur;cdby a burning vchiclein a accidcntresults is considcrablydependent on the bu$ lateralnosition.

ffi

passenger Figure 13. Simplified to$t with rsducsd dummy massss Figure 14. Individual survival room for each

923 Experimental Safety Vehicles

In a study by the German Federal Ministry of Transport lsrr{iela:rl *r ! :rl{9r iett,srdrr:,14,,1, , " ! concerning thc technicaldevelopme nt of emergencyexit systems,evacuation tests with a children'sgroup (g to l0 ycals) and an adult group werecarried out in a long_ distancetravcl bus ancl a short-distancebus. During severalIest runs. the following main escapcdirectioni wereprescribed: doors (Figurcs l5 and l6),as well as two emergency windows on the left sirle (Figure l7). A platform was erectedin I'ront of the winclowsto avoid injuries causcdby jumping. Since thc emergenc-vscene shown {'ol the compartmentcliscourages hesitation in front of a free evacuationopcning, the platform was a protectionmeasurc( l0). I'heevacuation tcsts showed the following results: r .Escaperoutc: doors For each vehicletype, the evacuationwas finished alter abour half a minute (childrcn, long_distance travelbus: 40s). Two-thirds ofthe passcngersescaped through the r.cardoor. r Escaperoute: two emergencywindows, left side (2 and 4 sidewindow)

ryru;ffi4

Figure 17. Evacuation through an gmergency window

f)estroyingthe window glassand removingapproxi_ matcly 90 percentof the window surfacerequired l5s, equally l'rtrsingle- or double_glassedwindows. Half the adult group left the vehicle by cachwindow within lessthan Imin (52s). Figure 15 Evacuation rest through the doors with an It seemsimportant that. in caseof alternativeescape adult group and a short-distance bus ro utcs,thc doors espcciallythe rear door_are prcferred. As a result,a stoppageis causecl in front ol thc reardoor, whercas the capacity of the other exits is not fully exploited. Improvements will bc possihle for thi crgonomicdesign of theexit aids, for childrenin thedoor areaand for adultswith accessto cnlergency windows. As the most cl'fectivemea$ure, the internaldoor accesrareas should be kept free (tickct barrier.s,folding sears,etc.). For a norrnal positionof the vehicleand an escape route to one sidc,the evacuation 'l'he tirneis lessthan lmin. relative rcquirernentfor airplanesis gOs.This is basedon the toxic effect ,\, of fumes,which dctermines the escapetirne of possiblyinjured pa$sengers,Up to now, accidentanalysis has not yct broughtsccured tirne values for vehiclccvacuation. A comparisonof internationalconstruction regulations concerning bus emergencyexit systemsshows that, Figure 16. Evacuationtest through the doors with an besidesLhe minimum requirementsfcrr vehiclc construc, adult group and a long_distancetravel bus tron,there exist alternativcs for a grcatnumbcr of other .Sectrbn1. TechnicalSesstons technical solutions. The position of the individual vehicle,its use,and passengerbshavior, emergencycxits and the neccssaryopening by fctlding This study hasmade it clearthat improvementsof bus out. remov'ing,and destroying(tool!) require detailed safetyare necessaryand possible. knowledgeand ability of thc bus paliricngcrs,which, in general.is not given. In contrastto constructionregula- tions for airplanes, there is nced of an cffectiveness References rcquirementfor the busemergency cxit system,based on the requiredevacuation (ime. l. StatistischesEundesamt, \ffiesbaden: Statistisches From the frequent use of doors, these must range Jahrbuch.1982. '*Test equallyas an elementof theemergency cxit system.The 2. Rompc. K., and B. Hei/Jing, proceduresand mounting position of thc emergencydoor-activating evaluationcriteria I'or thc handlingcrharacteristics of " devicemust be determinedon a standardbasis within a heavycommercial vehicles. limited areafor visionand handlingby the standingbus 3. StatisticschesBundesamt, Wiesbaden: occupant,This devicenrust be securedagainst unauthor- Strtr#enverkehrsunfdlle,Fachserie 8, Reihe3,3. "l'ossibilities ized use (thresholdof shrinkingfrom an impulsefor 4. Rompc, K., and H.J. Kri.iger. of action).An emergencydoor at thcvehicle's rcar could be dcvcloprnent in bus sal'ety," lst IAVD-Congress, an additional main escaperoute. Gcncva.February 22-24.1984. Thc rigid sidewindows consistof singlesecurity glass 5. Kriiger, H.J., Ciestaltung des Bus- and guaranteealso the structuralrigidity ol'the vehicle Fahrerarbeitsplatzes.IIMV, FP 7816/2,tlcricht dcs compartment.As a result.opcning each of thesewindows Institrrtsfijr Verkehrssicherheit,'[UVRhcinland, by destroyingit isgiven as a technicirlsolution and could 1979. mean a most important capacity increasefor the 6. K rriger, H.J., Bestandsaufnahmeder Inneren emergency exit system, The neccssaryemergency SichcrheitvonBussen, BMV, FP 7816iI, Berichtdes hammer -availableonly within vision and handling Instituts ftir Verkehrssicherheit,TUV Itheinland, rangc-raisesa rcasonableexpectancy of clfcctivencss, t97q. also for nonsper:ialists 7. Krtiger, H.J., Priifverfahrenfiir KOM-Fahrgastsitze Emergency holes in the roof could be an efficient als Riickhaltesvsteme,BMV, FP L8001,Bericht des escap$route with a minimum climbingheight, especially Instituts l'iir Verkehrssicherheit,TUV Rheinland, from vehiclesin a lateralposition. l 983. "An The improvementof passengersafety must bc proved 8. Rickey,Stansif'er, analysisof acciclentsinvolving with an efficiencytest of the emcrgcncyexit system. bussesand an assessmentof the needfor safetybelt Subjectto testmt: thods still to bedcternrined, a limiting requirementsin such vehicles,"Proceedings 22nd valueof 45sseems possible for evacuatinga complctcly AAAM Confcrence. "Aus occupied.upright-standing vehicle. 9. Walz, F'., der [Jnfrll- und Vcrkchrsmedizin," tt is required also for developedbus emclgcncyexit Automohil-Revue,Nr. 4tt, 1978. systemsthat the passengershave good knowledge ol'the 10. Kriiger, H.J.. Notausstiegein Kraftomnibussen, details. Thereforc, it seemsimportant to instruct bus BMVi BASI, FP 1.8306,Statusseminar, MUnster, passengersregarding thc crnerge ncy equipmentof each l9it4.

Heavy Truck Safety-\ryhat We Know

Henrv E. Seiff medium or heavy trucks. Only l8 percent of thesewere occupants of the trucks themselves:82 percent were Motor VehicleManufacturers Association pedestrianser occupantsof the other vehicle.The greatestnumber of combination truck accidentstakes place on two-lane rural roads. Single-vehicleaccidents Abstrnct are responsiblefor 70 percentof heavytruck occupant fatalities.Doubles and heaviertrucks appear to heas sale The overall highway fatality rate hasdropped almost as other heavytrucks. Itollover and eiectionare respon- continuouslysince 1925, lrom 20 to 2.5per 100million siblefor thc greatestnumber of truck occupirntfatalities. milesof travelin 1984.Still, the almost 44.000 fatalities in Whenasked about hcrtop priority asthe new Secretary "There's 1984can and will be decreased.In l9li3. 5,475of the of Transportation,M rs.Dole replied. no higher " 42,584 highway fatalities were in accidentsinvolving mandatefor the Departmcntthan to promotesafcty. . . .

925 Expe rlme ntal Safety Ve hicl es

The Secretaryis particularly concernedwith heavy truck involving medium or targertrucks, that is,ali trucks safety. over 10,000lb grossvchicle weight rating. Scvcralyears ago, the Motor VehicleManufacturers Ol thcsc 5,475fatalities, only lg percentwere drivers Association(MVMA) summarizedthe stateof heavy and passengcrsin the trucks themselves;g2 percentwcre truck safety'rcsearch in its presentation,,.Heavy Truck pedestrians or occupants of the other vehicle__the Safety .The Nced to Know." lt emphasizedthe urgent passengercar or light truck^_in a multivehicleaccirjent. need for adequatesafcty researchas a tbuntjati0n for Among the truck occupantlatalitics, 735 wcrc occu_ improving hcavy truck safcty.lt is appropriatenow to pantsol combinationvehicles, usually a tractor_semitrailer follow up with a summaryol'the thingswc have learned combinirtion,Two-hundrecl and forty-four wereoccupants since that time and to placc the heavy truck safety of straight trucks(2). problenrsin pcr^rpective. Since 1979, firtalities in medium and heavy truck I n reviewinghighway fatalities and fatality ratesfor all accidents have generally been dccreasingas have all motor vehicles,we $cethe extraordinary saf'ety gains that highwayfatalities (Figure 2). From 1976through tg79, have been made over the past 60 years(Figure l). The the increasein truck accidcnt fatalities paralleledthe fatality rate (personskiller:t per 100million vchicle_miles increaseI'or all highway vchicles(the quality of'the of travel)has dropped almost continuously I'rom lg25to National Highway Traffic SafctyAdministration's Fatal the presenl from ncarly 20 to 2,5 in lgg4. Although Accident ReportingSystem data on truck accicJentsin vehicle-milestraveled have constantly increased, with the thoseearly yearswas questionablcrso we havereason to exceptionof World War t I anrja shorrtime after thc 1973 belicvethe relativelylow numbersof fatalitiesin 1976 and I97tJ and oil shortages.the total number of highway 1977may be understated). deaths pca ked in the late I 960'sancl early I 970's.The 1,ss1 1984marked a 22 percentdecrcase in deathsfrom the high year ol l972,despite a 36percent increasc in vehicle_ milcstraveled( I ). 3 475 U t

t 50 I E = = 979 z.p

te76 19n E 1978 t97' r9E0 tgat t982 15N3 'Truckt6v.r , t0mtbs trore vlhc6F.cht rlxng SOLrnCt to,rlsa N,rbh:r i:rnrpl h trrrlr4 rdArJy.,. FATALITY BATE N,liffi;^,," Figure2. U.S. fatalities-medium and heavy truck accidents

Part of the recentdecrease in truck_relatedfatalities Figure1. U.S. motor vehicle accident fatalities, was ccrtainlydue to the businessclownturn of the past 1925_1984 few ycals and the coltsequentdccrease in truck milcage. However,comhination vehicle_rniles dropped less than I Although we can be justly proud of thesefigures, we percentfrom 1979to l9g3 while fatalitiesdroppcd l5 stillhad almost 44,000 fatalitics on our highways gg4. in I percent,so therehas becna real drop in truck_related We belicvcwc can and will lower this numberin future fataliticsthese pirst I'ew years. years. The vast majority . of the medium and hcavy trucks The reasonsfor decreasesin both the fatality rate and involvedin latal accidentsarc tractor-semitrailer combin_ total fhtaliriesinclude safer vehiclcs, sat'ety belts, highway ations(3)( Figure3). Although dor.rbleswcre allowed in 36 sal'ety implovcrnents, child restraints,better medical Statesin I 98I , Ior example, dou bles and triplestogether care,the 55mph speed limit, the imposition of thcFederal wcre rnvolvedin only 3 perc'cntof the latal accidcnts Motor Vchicle for SafetyStandards, irnproved dr.iver skills that year. and attitudcs,and the antidrunk driving campaignof Combination vehiclesas a group havea slightlylower recentyears. We are doing betterand can be espccially accidentrate than do passengercars, but a substantially proud to seelhtalities continue to drop at a Limcwhen highcr fatality rate (Figure4), Although we havea lot Americans are switching to smaller, lighter cars, and more to learn about why this ilt true, sornethings we do truck sizeand weightare increasing. know. Of the42,584 highway latalities in 1993.the latest year Bccauseof the wicledifference in massbetween a heavy for whiclr wc havedetailcd data,5,47 5 werein irccidents truck and a car or pickup truck,a multivchicleaccident

926 Section 4. Technical Sessions

SingleUnir 3,63A 24 Tracror-Semi...... ,...9,9i7 66 DoublesTriples ...... ,,, 4SS o Bobtarls , ,..,,.... 383 S fP Olh€r,Unkndwn .,.,.,,,, 631 4 Ti

Tolal ...... ,,, 1S.019 100 i{ Pq

SUFCF rruc^i tnv&d d Fatat Aedrfs. lS&-Bl b; Cr,+rdn and Psfirs. UMTal. Vanabrs tSj !1i Fi Figure 3. Types of trucks involved in U.S. fT1 [T,.H - fr accidents. 1980-1982 l,:,:,.,:,.,.,ru qRSAX UAOAfi UhSAH UFEAH Lrflrlao ua sTArE us sT.rE ro(AL ^CC[S$ TUTTLLTIE I'IAAE OTFIH 27i" ------+l f-73j" sOUrcE f*M m cffinrr v.h*rd F Frbr ksnrt i975.\98r Wu[u dr rr UMrRI tror. !.J

FATALITY FATE Figure 5. Where do combination multivehicle fatal accidents take place? (1976-1980) I !t I t xi ) t t c G Multivehicleaccidcnts represent 70 percent of the fatal rT G I heavy truck accidents,but only 30 percentof the truck d E occupantfatalities(5). Truck accidcntsarc most dangerous to the occupirntsof the othervehicles involved. We mentionedearlier that doublesand triplescombined

cAFa ColgrnATld{ cAFS COCBTtAItOt were involvcd in only 3 percentof mediumand heavy VEHEIES vEhrcLEs truck fatal accidcnts.Unlortunatcly, information is not availableyet to allow a deiinitive safetycompirrison of Figure 4, U,S. accideni and fatality rates for passenger tractor-semisand doubles operated under identical rs and combination vehicles, 1983 condititlns.The studiesthat havc bccndonc produced inconsistentlindings. Four studicsfound the doubles accidentratc lowcr, two studiesfound it higher,and three involving those vehicles is especially dangerous to the found no significantdifference between the two kinds of light vehicleoccupants. trucks. Although cornbinationtrucks operate more mileson Alier cvaluatingstudie s donc by othersand all existing the Interstatehighways than on any other kind of data,the University of M ichiganTransportation Research highway, Figure 5 shows the greatestnumber of latal Institutehas concluded that the involvelnentratc of the accidentstakes place on two-lanc rural roiids. Bccause two typesot'trucks is rrearlythe same(6). vehiclesare traveling at highspeeds in oppositcdircctions The SuprerneCourt agreedwith the Universityof on these undivided highways,accidents can bc more Michiganin casesinvolving the operationof doublesin frequent and more seriousthan on Interstatesor othcr Wisconsinand Iowa. The Court found, "The evidence dividedmultilane roads. convincingly,if not overwhelmingly,establishes thirt the tlombination vchiclestravel 63 percentof their miles 65-foot twin trailcr combination is as safeor saferthan on rural highwat's(4),being rrsed primarily to haulgoods the. . .55-footse mi."(7) between citics or frorn farm or factory to city. This The use ol largcr and heavier trucks to increase accountsfor both a low accidentrate and a high fatality productivityhas raised qucstions about their safety,As ratc. Becausethere is lesscongestion on rural than on with doubles,studies have produced conllicting conclu- urban roads,there genera)ly itre leu,eraccidcnts. But, sions. Reviewingcxisting studieson the sub.)ect,the bccauseol'higher speedson rural road$,ench accident Ontario flommission on Truck Safetyfound that an tends to be more seriousthan in the city, leadingto a overall increasein safetycannot bc cffcctivclyachicvcd highcr fatality rate. by limiting,within acceptablebounds. the weight or size "l'hc Single-vehicleaccidents, involving such things as a of trucks. Comrlission noted that oncetrucks had truck rurnningoll a high-spccdhighway, rolling over, or reached a weightof from I 5 to 20timcs that of passenger hittinga stationaryobject like a tree,are responsible for cars.increasing the weight further did not seemto have 70 pcrcentol'the heavytruck occupantfatalities, even any ell'ecton accidentseverity(8). though they reprcsent only 30 percent of the fatal Clcarly, heavicrand lirrgertrucks can move freight in accide'nts. fewer vehicles,reducing fuel usage,costs to consumers,

927 Expeimental Sof*ty Vehicles

and the total milesof operationduring which the vehicle conducts detailed investigations of individual traffic is exposed to traffic hazarrh. accidents.From 50 heavytruck investigations,NTSB has Whcre the truck, the truck driver, or the truck's isolatedthese accident causation factors: opcrating environmentwere seen as contributingfactors r The driver to a fatal accident,thc flniversity of Michigarrfound 64 r Vehicle-brakingcapability percentwere driver-relatecl, 27pcrcent were environment_ r Vehiclerncchanical condition or highway-related,and 9 percent werevehicle-rclated(9). r Steeringor directionalcontrol When the truck driver contributed to the accident, r Coupling devrces driving too fast was identifierJ27 percent of the time; r Fuel systems failure to keep in Ianeor driving on the wrong sidc,lg r Truck cab environment perccnt;carclcssness or inattention,I7 percent;failure to In three-fourthsof theseinvestigations, NTSB identified yield or to obeytraffic controls,l3 percent;and improper the truck as the primary causeol the accidentand, in following or passing,7 percent.Drowsiness ancl fatigue virtually all 50 accidents,thc sizeand weightof the truck were cited only 6 pcrcentof the tilne. contributedto the severityof the injuricsand the number The combination vehicledriver in a fatal accidentis of fatalitics. Driver bchavior was either a primary or involvcd with alcohol only 4.5 percent of the tirne, secondarycausal I'actor. This ledto NTSB concernahout compared to a 46 percent involvement in all fatal licensing,training, experience,alertness, understanding accidents(I 0). of vehicle systems,physical health, and the driveris When highway or environmentalconditions contribute environmentin the cab(15). to the fatal combinationvehiclc accident, obscured vision Earlier we showedthat 82 percentof the fatalitiesin and swerves,due to weatherconditions, highu,ay design mediumand heavytruck accidentswere not theoccunants ploblems, etc.,are identifiedas the maior factors(ll). of the large truck. They were generally occupantsof When vehicle condition wasidentilled as contributing parrscngercars and other Iight vehiclesthat colliderJwith to a fatal accident,the brake sy$temanrj tire and wheel the largetruck. ln summary- problems accountedfor nearly 80 percent of the con_ r The fatalitiestake placein the 70percent of fatal tributing factors(12).Although only percent 9 of the accidentsinvolving largetrucks that combination are multi_ vehicle I'atal accidentswere identifieclas vehicleaccidents. involving vehicle-relatcdfactors, thcre is no doubt that in r The accidents are especiallyserious becauseof many instancesgood vehicledcsign antl maintenancecan the largedisparity in massbetween a largetruck allow a driver to safelycompensate for his mistakesand andthe other vehicle involved, usually passenger avoid a an accident. car. The experienceof the Bureauof Motor Carrier Safety r Almosr half of the multivehicleaccident fatalities is importantin evaluatingthe rolc of vehiclecondition. occur on rural, two-laneroads where 90 percent The Bureau inspected over 33,000interstate trucks in arein head-on,angle, ..out anrJsidcswipe accidents(16) 1982.It put 37 perccntof thosevchicles of "imrninently service" This suggeststhat further separation of vehicles for hazardous"mechanical nroblems. The traveling in opposite directions, especia[y vehiclesof Bureaufinds that almost half the maintenanceproblems suchdisparate masses as passenger cars and largetrucks, that led to putting vehiclesout of servicewere related to should he investigated,As prool'of the effectivenessof brakes,lollowed closely by lightingor electricalproblems, separatingtraffic directions,one has only to look at the tires, and wheels(13).While the Bureau selectsvehicles divided, Iimited-accessInterstate system, which is credited for inspectionbased on its estimationthat they are in with having savcd approximarely 4,600 lives in l9g3 greatestneed of inspection,,,out-of-service" percentages aloneby cutting thefatality ratein half compared wcrc not with all that much lowcr when vehicleswere selccted at tJ.S.highways(17). random. Rollover is involl'ed in 50 percent of combination The Bureau of Motor Carrier Safety'snew State grant vehicle driver fatalitics, with ejection found in 34.4 program, (Motor Carricr Safety Assistanceprogram), pcrcent (Figure 6). Extrication accidenrs(22.4 percent) combinedwith the Stateand llrovincialreciprocal inspec_ arethose in which the victirrrmust bephysically removed tion program of the CommercialVehicle Safety Alliance, from the damageclvehicle. In sornecases, the victim was will insurethat many more vehiclesare insrrcctedon the crushedwithin the truck cab. Fire is found in few truck highwayfrom now rtn,The Burcaufound, in a four-State accidentsoverall but is presentin about 16 percentof pilot study of incrcasedtruck inspections,a 25 to 52 accidentsthat provc fatal to the combination vehicle percentreductirrn in truck accidentsfrom l97g ggl(14), to I occupant-about I 25 casesannually( l g). If theseinitial resultscan be projectedto a nationwide The percentagesgiven add up to more than 100 program, we can expecta substantialdecreasc in truck percent. In many accidents,more than one event accidentsin the future is involved, such as a rollover and ejectionor The a fire and National Transportation Safety Boar

928 .Section4. Technical Sessions

agencies,organized labor, industry trade associations, vehiclenranufacturers, suppliers, and universities. Flollover 59.0% Our challengeis to usebetter data and betteranalysis Ejection 34.4 to find innovativeand constructivesolutions. Extrication 22.4 Fire 16.1 References Noneof the Above 15.1 l. National Safety Council, Accident Facls (Chicago, 'lransportation, I984),p. 59,and U.S. I)epartmentof TotalNumberof Federal H ighway Administration, Highu,a.vStatistics (Washington,D.C.: U.S,fiovernment PrintingOffice, Fatalities 1964 'fable 1983,and earliereditions), VM-1. 2. Interview with Grace Hazzard.National Centerfor SOUFCE: Universityof MichiganTransportation Besearch In- Statisticsand Analysis, National Highway Traffic - $tituts fromNHTSA Fatal Accident Beporting Systems data, SafctyAdministration, Washington, D.C., January 24.r985. Figure 6. Combination Vehicle Driver Fatalities, 1980- 1982 3. Carsten,Oliver, and LeslieC. Pettis,Trut:ks Involved in Fatal Accidents, 1,980-82,Ann Arbor, MI: Researchhas provided substantialinformation on the University of Michigan Transportation Research typesofaccidents that provefatal to truckoccupants and Institute.1985, variahle 106.1. pointedout a numbclof waysin whichlives can be saved. 4, Federal H ighway Adrninistration, Highwa.1,,Statistits, Foremost among them are sat'etybelts. Safety belts are TableVM-1. tailor-madefor the rolloverand ejectionaccidents, which 5. Clarke, Robert M., and Joseph Mergel, "Heavy causethe nrajority of truck occupantfatalities. Research truck occupantcrash protection-a plan for investi- sugge$tssafety belts could saveperhaps 40 percentof the gating ways to improve it," SAE Paper 821270, combinationvehicle occupants who die eachyear and Indianapolis,Indiana, November 1982. reduce injury severity in perhaps 70 percent of the 6. Chirachavala,Thipatai, and.lames O'Day,,4 Combina- serious-injuryaccidents( l9), Since1970, thc useof sal'ety tion oJ' .Acrident Chararleri.sti(s and Rates .fitr beltshas been requircd in irrterstatetrucks hy thc Bureau Comhination Vehicles wilh One or Two Trailers, of Motor ClarrierSafety; yet today, only about 6 percent Ann Arbor, Ml: Universityof MichiganTransporta- of the drivers wear thern-less than half the userate in tion ResearchInstitutc, p,7, 1981. passengercars(2O). So, if we can get truck drivers to 7. Kassel,et al,,vs. Consolidated Freightways, 450 U.S. buckle up, a significantnumber of livescan be saved, 661,1981. "Report We now know far morc about highwayaccidents than 8. Uffen,Robert J., of theOntario Commission we didjust a few yearsago. But thereare many problcms on 1'ruckSafety," Ontario Ministryof Transportation still to investigate.For example,we havelittle dctail on and Communications,p. 159,1983. accident exposureby type of vehicle"A wide range of 9. Wolfe, A.C., L.D. Filkins,and J. O'Day, Facthook trucks, l-ravingspecializ-ed vocational uses, travcI on on Comhina- Vtthirlesitt Fatal Accidents, 1975-198 I , dilferentkinds ol'roads,with varyingloads, at various Ann Arbor, Ml: Universityof MichiganTransporta- timesof day, underall kindsof environmentalconditions. tion ResearchInstitute. 1983. Tables 2.10.2.17. and Until we can analyze this exposure inlbrmation, it is 3.6. impossibleto pinpoint cxactlyhow to identifyand break 10. Ibid, Table 3,7,and U.S. Departmcntof Transporta- the irccidcntcausation chain for specilickinds of vchicles tion, National Highway Traffic SafetyAdministra' "National and accidents.We need more detailedinformatron on tion, accidentsampling system 1982," drivers, highways, vehicles,accident forces, handling, Washington,D.C., 1984,Table 6. brakrng,and stabilityin crisismaneuvers, and specificsof I l. Wolfe. et al.. Fat:tbooli,Table 2.10. thc accidents themselvcsto considcr poter-rtialaccident r2. lbid,Table 2,17. counternrcariuresintelligently. t3.U.S. Departmentof Transportation,Federal Highway Researchis underwayon a wide variety of subjectsto Administration, Bureau of Motor Carrier Safety, "1982 get these answers,including continuing accidentdata roadsidevehicle inspection report," Washing- collection and analysis;combination truck braking, ton, D.C.,pp. 6,10,1984. -l-ransportation, coupling, and hanclling,vehicle crashworthiness; and [J,S.Department of Federa]Highway ways ol'encouragingsafety belt use. Administration, Bureau of Motor Carrier Safety, "Commercial Researchis bcing conductedor sponsoredby virtually motor carrier safety inspectionand everyoneinvolved in the trucking industry,including weighing demonstrationprogram, interim report," insutancecompanies, motor carriers,r'arious government Washington,D.C., pp. 3,4,1981. Experim ent aI Safety Vehlcles

15, Kissinger, J. Peter,National'l'ransportation Safety 18.Computer run of University of Michigan Transporta- Board, to aurhor, April 26, l9tt4, MVMA files, tion RcscarchInstitute data filesof'heavy truck fatal Washington,D.C. accidents,MVMA ljlcs,Washington, D.C. 16. O'Day, James,"Commercial "A vchiclesafety issues," 19.Ranney, Thomas A., study ol' heavy truck National Highway Safety Symposiumpaper, occupantprotcction: accident data analyses," Calspan Williamsburg,Virginia, Febr.r.rary28-Marcrh l, 19g4, Ficld Scrvices,Inc., UutTalo, New York, p.6t), 1983. Table L 20.Clarke and Mergcl, Heav.1,Trut:k Ot:cupanl (rash 17. National SafetyCouncil, Accident Fat:ts,p. 44. Protettion, p. 17.

HeavyTrucks Aggressivity for RoadUsers- In Searchof ImprovedSafety

Maryvonne Dejeammes heavy vehicleswill emergefrom the analysisof national ONSEIt-Laboratoire desChocs et de statistics( 1982files) as well as from the dctailedstudy of Biom6canique accidcnt cases(ONSER bidisciplinaryinvestigation). The first lines of an evaluation rnethodologywill be presented Abstract in the caseof a front crashheavy vehicle/car.

For many years,heavy trucks have accountcdfor a GeneralTraffic Conditions large part of the damaging road traffic in France.To determincways ol' improving heavyvehiclss so a$ to Heavy vehiclesare differentfrom carsby their assign- dirlinish the sevcrescore of accidents,the national ment to goodstransportation or peopletransportation, statistic file ot' injurious accidcnts in l9B2 ancl the and conscquentlyby their largermass. They are divided ONSER bidisc:iplinaryinvestigation file have been into threc categories:light trucks or dcliveryvans of less analyzed.The most important risks aff'ectpedestrians, than 3.51.hcavy trucks of 3.5to 38t,and publicservice two-whcclcrs,and car passengers. vchicles(transporting more than ninepeople) It appears rcscarch on treavy vehicles should be Thc followingtable shows the numberol'vehicles and undertakcnat first for- covereddistances: r Improvinglateral vision r Fitting up of heavyvehicle flanks to avoid falls Covered underrear wheels and to limit underrun distance,/vear r Fitting up of heavy vehicle front structureto Category Number in kilometers reduccits aggrcssivityagainst passenger cars Passengercar The purposc of sal'etyrneasures complcrnentary with 20,420,000 l3.OOO lighttruck energysavings nccessity should bring about realizahle 1.51to3.51 1.060.000 zE,OOO solulions. heavytruck )3 51 45o.ooo 15,oooto 7o,oo0 publicservice vehicte 76,000 25,000to 62.00O Introductiorr Risks related to the tralfic of heavy vehiclescan be For many years,heavy vehicles have bcen considered a definedby thc involvemcntoi've hicles and the number of factor of dangerousroad traffic in France. Bccauseof fatalities related to the nurnber of vehiclesX cover.ed their large mass,these vehicles contributc to Ihc severe distarrcein kilometers: harm inflictedon their opponentroad uscrs. Upon action of thc FrenchDe partment of Transport,the Clommittee "For 1980 HT(>3,51) car named a better safetyof heavyvehicle traffic" has recommcndedrescarch thcmes to irnprovethc saletyof VehiclesX km 20 10e 2bO1Oe heavyvehicle occupants and other ruad users. lnvolvernent,/l06km O.BS 1.12 It is then necessaryto define thc most dangerous Fatalities,/ 108veh,/km I 1.0 4.0 accidcntsituations with respectto thc difibrent categories of roacl uscrs-pcclestrians,two-wheel riders, and car So, the rate of involvementof carsis higher than that of occupants.Research axes to diminish thc aggressivityof heavy trucks, but the nnmher of i'ataliticsrelirtcd to

930 Section4, Technical,Sessmns vehiclekilometers is 2.75higher in accidentsinvolving a Front heavytruck. Left front Right front Lateral GeneralAccidental Statistics left + right Analysisof tlOverturn-wrecked Rear lateral To take into account the types of heavy vehicles lsfl + right II involved (different by their design and mass), the Rear categoriesof road useropponcnts, atrd eventhe type of trafficnetwork, an analysiso[the statisticaltile RESUM E, thc basis datrr of the National worked out from Front = Front + Left and Right Front Constabularyand the National Police,has beencon- '[his l.ateral = Lateral Left + Right and Rear Left + Right ducted. combinedfile has beendrawn up from the lorms on injurious accidentsoccurring pac,h year, and it Accidentseverity can be determinedby the percentage hassome limits from its homogenouscoding and simplihca- of Iatal accidentsin relation to the total of'injurious tion; Aggressivity will he given by the ratc of r A maximum of three vehiclcsis reported in a accidents. killed and severelyin.lurcd (other than heavy same accident (l percent of accidcntsirrvolve external per accident. more than threevehicles). vehicleoccupants) distribution of accidcntsin which at least r A maximum of two roads is dcscribedfor an The overall was involvedtor 1982is shown in accident. one heavy vehicle l. r A maximum of [our occupantsis reportedin an Figure accidcnt.Registered occupants are thoscwhose iniury severityis the highest. These limitations may be acceptedto analyzc the AccidentsInvolving Heavy problemof heavytruck opponents.Some reserves mu$t Vehicles/Pcdestrians be made for analyzing accidentsinvolving a public servicc vehicle becauseof the numbcr ol occupants registercd. In this category,2,620 accidents resulted in 297 fatirlitiesand 76-5severely injured pcdestrians, The overall externalaggressivity is then of 0.40. GeneralPresentation The implication is relatedmainly to the road network:

The analysisof the file RESTIME has beenmade for 1982,which shows 222,047injurious accidents,among heavvvehicle was involved in 21,957cases. whicha LesionSlAccidents Faial Accidents We take into accountheavv ve hicles (l{V) classifiedin threecategones; r (1.5 Light truck to 3.5t)noted 1".T, Involvinq d r Hcavy truck (lorry and tractor*trailer)noted Hoavy Vehicle H,T. r Publicservice vehicle (rnotorbus and motorcoach) notedP.S.V. The road useropponents afe: r Pedestriansnoted Ped. UseB Oppos6d to Hesw Vdhicl66 H68vy Vehicle Occupsnt8 r Two-wheelersnoted 2-Wh. 8.310Fatallv and SeriouslvInjureo ?,AZ Fa\allyand Scriousty Injured r Passengercars notcd Cars The traffic network is divided into threetypes: r Ilighway r Nonurban road I r Urban area Data on collisionconfigurations are more difficult to analyze.and the combinationof impactzone ol'vehicle and impactdirection is no( considered reliable enough in this file to insurea good description.It wasthen decided "vehicle to addressthe parameter impactedzone" with the followingdistinctions: Figure 1. Accidents involving heavy vehicles

931 Experimental Safety Vehicles

P6d€striEns The analysisof the heavyvehicle zone impacted by the two-whccler shows unquestionable No. of Fatel Savsrslv an differencebetween I 98? Ecc. acc, Killed injured the catcgorieso{ vchicles:

Highway t7 tO tO 6 O.94 Nonurbdnroad ?61 14 74 lO2 O.7O Urbanaraa 2,371 Z1g 213 657 0.37 % 2-wh lmpactedZone Fat,sevjured Front Rear Ldt.Front Lat.R6dt Total Lishttruck lJrban collisions representg0 percent of accidents. 59 6 l9 t6 tOO% Heavytruck 43 I ?3 ZE 1O0l/" Whilethey show a not too highaggressivity (0.37 cxternal Pub,serv.veh. 57 I 20 lS toe7o killed and severelyinjured people pcraccident), they total 82 percentof killed and scverelyinjured 'l'able pcdestrians. I gives a detailed description of accitlents As for the category ol heavy vehicles,evcn if public involving heavytrucks/ two-whcelers. servicevehicles run a lot in urbanareas, light trucksand The highest frequency and the highest severity of heavy trucks are thosc that causethc rnost pedestrian impacts againstheavy truck flanks in comparisonwith victims. light trucks and public servicevehicles can certainlybe explained by the designof their structurerr(presence of Pedestrians side fairingsflush with axles). I 98? No. of Faral S6v6r6lv acc. acc. Kiilod injured Aggrds8ivity

Light truck l.OB7 tOO 1O0 AtB 0.38 AccidentsInvolving HeavyVehicles/ pas$enger Heavy truck A24 1 SS I ES Z7O o.52 Cars Fub.sBrv,veh. 729 42 42 177 o.30

A total of I 1,473accidcnts resulted in I Note the higher aggres.sivityof heavytrucks, a figure , I 39 fatalities and 4,033 severelyinjurcd car passengcrs. derivedfrom numerousand scverecollisions on cennec- The external aggressivityis 0.45, similar tion roads passingthrough an urban area. to the one for two_wheeler opponents,but car pa$scngervictims are 2.5times more numclous. Accidents Involving Heavy Vehicles/Two- The implication is more f'requentin urban areas,but Wheelers the gravity is much more important in nonurbanroatls as shownbelow: A total of4,499 collisionsresultcd in 3g4fatalities and I,682severely iniured two-wheel passengers. Consequcnt- t"' o"**"*l"Ji,, l gez No.of FEt6r ly, the overallcxternal aggressivity is (),46,which is a acc. acc, Killsd injured Aggr6ssivity slightlyhighcr ratc than for pedestrianopponents. Highwoy 409 56 69 t AB O.S1 The implicatiorrdepcnds Nonurban -l-l1 on the roarl network with a roads 4,564 660 Z,ZiO 0.66 Urbanar6a large I'requency,in urban areas: 6.500 26? 2S4 f,OSS O_30

Heavytrucks are more frequentlyinvolved and exhibit Two-wheeler the highestaggressivity:

1982 No. of Fdtdl Severety

acc, acc. Killed injured Aggressivity t"t o"*t"J"nuTi,, HiqhwayZt66BO.Sz r 98? l{o.of Farar Nonurban roads 887 143 t46 494 O.tl . Ecc. acc. Killed injursd Aggressivity Urbartarea 3,585 241 242 I.l9O O.4O Lisht truck 3,453 169 147 l.OO7 0.33 Hsavyruck 8,675 ISZ AS7 Z,EB4 O.54 'l'he Pub.serv.vah. 1.348 73 96 gae aggressivityrelatcd to the vehicle category is O.32 roughly comparablc to the one for accidenrsagarnst "fhe pedestrians,but it has to be noted that severeaccidcnts analysisof the accidentconfiguration has been involving a heavytruck prevail. rnadcby distinguishingbetwccn the variousparts ol.the passcngcrcar that were impacted-front, side lelt and right, rear.The impactedparts of the hcavyvehicle were Two.whE6ler detailed in the cornputerizedsorting accordingto the 1982 No. of Faral Severely abovepresentation. Table 2 surnmarizesregistercd figures acc. a<;c. Killed iniured Aggressivrty accordingto the categoryof heavyvehicles. Light truck g0 1,773 90 678 O.43 The fronto-frontal collisionaccounts for morethan 40 Heavy rruck 2. I EO 27 I Z7b 830 0,S 1 Pub,serv.veli. percentof killed and injured car passengers 576 29 29 174 O.A5 for the three categoriesofheavy vehiclcs. Collisions between passcnger .fecdon 4. TechnicalSessfozs

Table l. Heavytruckltwo'wheeler collisions

1982 A ? n*o 469 No. of acc. 765 192 473 Fatalacc. 111 12 b5 65 65 65 Killed2-Wh 113 -1413 r88 Sev,ln.|,2-Wh 322 167 253 Killed= Sev lnj.2'Wh 435 87 232 ?q ts 21 23 Killed = Sev. Inj 2-Wh 057 045 049 0s4 per acc.

' 9% are not deterrtrirred

Table 2. Heavy vehicle/pass€nger cat collisions

I 982 fl n I fl.,rOthers Accidents 1,s02 590 177 ?o2 720 262 L.T. Fat.+ Sev.Inj. 624 ?24 38 22 173 73 car Car 19 15 6 Ext.Agg. 040 o38 021 011 o.24 0.28

Accidents 2,273 1.046 514 363 1.689 7SO H.T. Fat,+ Sev.Inj. 1.455 612 225 88 B4B 353 Car Car 41 17 24 10 Ext Agg. 064 0.59 o44 0.24 050 045

Accidents 555 273 83 84 243 107 P.SV. Fat. + Sev Inj. 224 8l 28 5 70 29 caI Car 51 l9 16 7 Ext.Agg. 040 0.30 o34 006 o.29 o.27

morethan 3.5tand publicservice car and heavyvehicle flanks and betweenheavy vehicles whereheavy trucks of 20 percentof vehicles( motorcoerchand motorbus)wcre involvcd from and passengercar flanks represetrtncarly "passengcr The car" is uscdfbr atry killed and severelyinjured car passengersin each case' 1975to l9lJ4. term as a lirrtousinc,break, or coupe' However,it hasto be notedthat heavytrucks differ from vehicleequipped dil'ticultto get precisedata on material light trucks and public servicevehiclcs because accidents Since it is I'ehicles,whose occupantsare rarcly againsttheir flanks aremore severe'As previouslystated damagc to heavy beenfound in the files: for two-wheelers,explanation must be found in the injured, it has chassisstructures that stand high and are recessedfrom . 25 accidentsfront car/front HV the loading frame and make underrunp

933 Experim ental Sdfetl Ve hic I es

The accident severity noticed in the files of the This table emphasizesthe bidisciplinary sur!'ey' violenceof impact with a is higher rhan that found at the completc intrusionol'the compartnrent in l0 cascs,along national level.This is evenmore cnhancecl for thefronto_ with the increasingin jury severityirccordirrg to the Iiontal configurationbetween a passenger levcl car and heavy of compartmentintrusion vehiclc;l2 out of thc 25 accidentsare fatal, 1'hedescription of lesions,which is availableexcept Thc lesionirl score is given on Tablc in 3, where a the I0 casesof fatality(no autopsy), distinctionis madebetween givescvidence ol the front and rearoccupants and impact violcnce against cumpartmentparts such as wherebelt-wearing by car passengersis mentionecl: stecringcolurnn, dashboartl,windscr.cen irutn., pcdals.

Table 3. Car passengorsinjury severity

Severely Lightly Injured Injured Uninjured Afs >3 Ats I _2 Belted front occupant 3 unbelted front occupant 7 Front occupant 4 belt-wearing unknown Rear occupant 5 Total 19

It is then shownthere are more killedoccupants among and even an outer unbeltcd object (heavy truck struature).Any ones.The sevcrityof thiscollisioniype fo, .ear body part is then likely to he severelyiniured. occupantshas to be noted also. On the other hand, heavy vehicle Thesecollisions are characterized occupantsare very by thc well_known seldom exposed.ln risk of the passenger our sample,it appe,,rsthe injured car.to underrunthe heavyvehrcle pcople I.und in three heavyvehicles structure,which meansa limitation sustaincdresions of thc protective either on e.jcction(one ell'cct of the slightly injured) or during an 3-point belt due to thc reduction of the impactsubsequent to the oneagainst the passengcr decelerationzonc in thecompaftrn(j nt. Impacfclircctions car. During an impact againsta trce,2 f.ont passengers and underrnncases are drawn out by analyzingpasscnger of a motorcoilchsustained scvere in juries; car deformations.ljnderrun is definea durir,gan impact as tt,* casewhen againsta pole, l2 passengers the car is impactedabovc of a motorcoachwere tightly its rigid structures,1.e.. side_ inj urcd. mcrnbers,rnotor, and gear-boxunit. There are also various cafegories Impactsto the left are the of heavyvehicles in more nurnerous: this rarnple to draw out behaviortencJencies. It can r l.ront mcrelybe left impact; 12cases saidthat trucksof morethan I0t and tractor_ r Clenterimpact: g trailers do not show cases a vcry clilTerentbehavior, which is r Front right impact: 5 cases explainedby their similar front prolile. So, the fhct that front Casesof underrun structuresofheavy vehiclesare are mort: numerous(13 cases);6 not compatible with pas.scngercars,as well asthe l.atio accidentsoccurred without unrierrun, In the6 remarning of their masses,explains the severetribute pard cases,the underrun critcrion has not by car been asserted occupants.Howevcr, specds becauseof theirnportant late and .sev.crity,levels of these -l ral deformationso[ thecar. collisionscannot heasse ssed in a reliableway, either 1iom he relationshipbetwccrr rJerbrmations o| the vehicle availabledata or I'romprc.sent knowlcdge. As and its compartment an

' impactsagainst a rigid barrier.Catibrated tests thatwould years. The rear underrun guards provide a givea setof data on car deformationsand decelcrations certainelliciency. which coulcl be stillimproved are lacking up to now, and thc estimationof speeds by cnergy-absorbingdevices(2.3), before the impact and ol braking distanaesare not The work to be done now is to limit the aggressivityof unquestionablefactors. heavy vehiclefronts. The collision severityis in direct This accident case study, however, bears out th€ relationship with the geometryand the masscsol' the (on severity and frequency of left frontal collisions involved vehicles.As metrtionedby I'ranchini(4)'the passengers

935 Experimental Safety Vehie Ie s

Conclusion References

In France in I98?, 21,950accidents involving aheavy L Favero,J.L., S€curit6et conceptiondes poidsJourds, vehicle resulted in at least g.310 killed and severelv Cahierd'6tudes ONSER No. injured among pedestrian, 47, March 1979. two_wheeler,and co, op_ Ileermann, ..Behaviour Z. H.J., ol.pilssengercars on ponents,whereas mrlre than 2,g00truck occupant$were impact with underride guards,', killed or severelyinjuled. Int. J. oJ' Veh. Design,Vol. 5, No. I.2, pp. 86_103,19g4. The analysisof thecircumstances and theconsequences 3. Penoyre, S., B.S. Riley, and M. page, ..Desirable of theseaccidents has producedmeasures likely to lirnit structural I'caturesfor thc this heavytribute: designof iront and rear underrun bumpersfor heavygoods vehicles,,, Inter_ r Improve the side visual field offered to the truck nationalConference on Vehicle driver Structures,I fulechE Pub.,pp. r 139-t46,l9tJ4-7. Modify heavyvehicle llanks to limit I'allsof two* ,.Truck 4. Franchini, E., crash testing,"International wheclerson the trajsctoryof rearwheels and also Congressl-'tSITA, pp. 901_912,1970. to avoid car underrununder loading platforms ..Diminution 5. I)ocument L/TAC, de r Modify the heavy l.agressivitbdes vchiclefront to make it less v6hicules utilitaires en cas de collision avec des aggr.essivetoward passengerscars. especially by voitureiiparticrrlibres," A I'p S6curit6des vehicules, avoiding the underrun under rigid structures of flontrat 77114,Rapport final, 1979. thechassis and by providingan energy_absorbing 6. Johnson, W., and A.C. Walton, ..protection area of car occupants in frontal impacts with heavy lorries: Heavy vehicle traffic has been considereda factor of " frontal structures, 1nt. J . Impact f)esign,Vol. I unsafenessfor many years.Sel,erirl , No. countrics,like France, 2, pp. lll-12-3,1983. admit it is mostdesirable that solutionsto theaggressivity 7. Danncr, ..Results M., ernd K. Langweider, of an of heavyvehicle fronts and flanks be found. Thesesafety analysisof truck accident,sanripossibilitie.s measurescan be complementary of reducing to current priorities their consequences concerning discusscdon the basisof car to road traffic, such as energy savings.We proccedings truck crashresrs," 25thSrapp Car believeactual outcomeswill emcrge Crash fl-crminternational flonlercnce,pp. 903-950,lggl. researchbeing carried out at pre$ent.Evaluation Dro_ L Riley,8.S,,B.P. Chinn,and H.J. Bares,..Ananalysis cedures necd to be determined, which n"cessitotesa of ,, fatalitiesin heavy goodsvehicle accident, TR RL better knowledge of collision sev$ritiesto give a more LaboratoryReport 1033,lggl. realisticpicture of'trafl'ic accidents.

P.S.V. Rollover Stahilitv

D.M. White Introduction CranfieldImpact Centre, United Kingdom To get from safe,normal driving in a bus or coachto a Abstract fatal rollover accident rcquires a sequenceof events similarto thoseoutlined in Figurc l. It canbe scen there are two stageswhere governmental cfforts Nine busesand coaches may be made weretested to experimentally to reduce rollover accidents,anrl two further arcas in determincvarious parameters considererJ to aflectrollover which the severityof an accident,if it docsoccur. stability--.principally, spring mav be stiffness,position of centre reduced.Already significant gravity, legislationexists to minimise of and roll moment of inertia. Utilising these lossof control. Other factors,such as carel.ul roarj dcsirn data,a computersimulation of a typicalrollovcr accidcnt and layout, and trcating icy road suri'aces,may also was used to cornpare the relative performancc f,e of the addedto thc measurcslisted in Figurel. different vehicles ancl investigatc the effect of each However, coacheswill not usually roll over parameteron the rollover threshold. without Heightof the centre certain other circurnstances. of gravity Thcseare typically_ and, to a lesserextsnt, roll centreheight were r 'l'ravelling off the road onto a significantly I'ound to have the greatestefl'ect. inclined bank

936 Seetion 4. Technical SBmioas

Tyoico 5e,1',enceot Ailion8 Aim€d to EventsLeEdrng to F6ducB Fatalitist Their Oqcurrencs and Iniunes: /ror*^to

MinimrE€trcurronco qf lo6sot controlbY lrgidotion qn: . btokgg

. srsoring . mdximum capacrty I drivertraininB . fraxtmum 9pe0o I'\" . tilt t6Bl | 'r . maximum leid EnsounterCondinons GIOAAL TIE5 Which Otten Csuse rollov.r (given rollovor conditiom) bV Follover Minimi6e legislailanon: Figure 2. Mathematical model {12degrees of freedom)

Fleducdd€lormotion {givAfl rollovor) ECE contider- ing legithtiv€ tost tg snEuro odoquEtq 6utulv6l tqaae.

Fstsin DoEseng6rs{oiv.n rollovor). Re8irrcfi FF oosed hut n0 action.

Figure 1, Components of typical bus rollover accident

I Sliding sidewaysinto some form of roadside tripping obstaclc(such as a curb, low wall, or solt verge) Whether qp not a coach rolls on an inclinedbank would bealmost solely dependent on its statictilt limit, as measuredon a tilt test. The lirctorsaffecting whcther a givenvehicle would roll if it strucka curb with a given lateral vclocity are lessappafent and are the subjectof this paper.

Descriptionof ComputerProgram

The Rollover Accident Simulation Program (RASP) was developedto studyin detailthe designf actors that the propcnsity of a vehicleto roll over when it strikesa curb, low wall, soft vetge,or similar roadsideobstacle Figure 3. Suspensionlayout of mathematical model whileiliding sideways.As such,it assumesthe driver has already lost directionalcontrol and, therefore,the pro- pitch, gram does not include vehicle dynamics routines to freedom(that is,longitudinal, lateral, vertical, roll, model steering,braking, or accelcrationmodes. lnstcad, and yaw). Each axle was consideredto be a beam axle, the simulation begins with an initial lateral velocity freeto roll or displacevertically or laterallywith respect perpendicularto thecurb. I tnpact between tyres and curb to thebody. For a two-axlevehicle, this results in a 12"of occurs,and theensuing motion may or may not resultin freedom model. Simple modificationsto the program rollover. createda l5o of freedom versionlor three-axledouble- deckers. Mathematical Model Assumptionsand Featuresof Model The vehicleis definedby its massdistribution, inertial properties,spring and damping conbtants, and dimcnsions The i'eaturesincorporated in the modeI and assumptions as indicatedin Figurcs2 and 3. madein derivingthe equations of motionare as follows; The equations ol' motion were formulated by con- L The road surfaceis assumedto be uniform and sidering the sprung ma$s as a rigid body with 6o of horizontal,

937 Expeimental Sa-fery Ve hitles

2. The curb is positioned perpendicularto the vehiclc'sinitial vclocity. CONTACT 3. Pitchangle ol thc sprungmass is assumedto be FORCE small (that is, small anglcapproximations are .r,,. ) uscd:sin 0 * 0 andcosd+ l). 4. Axle roll anglesrclative to the sprungmass are also assumedto be small. 5. I'he relativeroll motion of thesprung mass and axles is assumedto take placeabout a roll axis that is lixed with respectto thc sprungmass. It is delinedby specilyingthe initial values ofthe roll centreheights at the front and rear axles.The roll axis is takcn as the linejoining thesetwo points. Weir(I) in the bus versionof a vehicle dynamics progrirm assumed that the vehicle ccntrsof gravity(CG) musrIie on this roll axis. This program,however, enables the C(j nosition to be del'inedinriepcnclenrly trf the roll axis. 6. Spring/damper units act at the tyre contact points wherethe forcesfrom the road and curb 0EFIECTl0tlra) arc applied,and also betweenlhe sprung mass Figure5. Representation and each of tyre/curb stiffnessnonlin- axle, simulating the suspensioncom_ earities ponents, Figure 3 shows in greater dctail the connection betwecn the sprung mass and an relative roll angle exceedsl jo. Similarly, the axle. Note thirt only one vertical spring is curb stiffnesstakes into accountthc limitecltyre employed (with an axlc rate stil'l\rcss)antl thc lateral stil'l'nsssand attcrnptsto accountlbr the roll stilTnessis provirled usinga scparatetorsional increascd stiffness when the curb contacts a spring. more solid part of the vehicle,such as a whcel 7, Linear characteristicsare usedfor every spring rirn. with two cxceptions: the roll stiffnessesand 8. Provision is also made tbr energylosses at the tyre/curb stil'fnesses are as shown in Fisures4 tyre/ curb contact(duc perhapsto ground or bus and 5, rcspectively. The secondaryroll siffness dcforrnation) by allowing plastic behaviour. models thc effect of bump stops when the This is cvident in Figure 5, wherethe dcflection increascswith constantforce ancl is not recovered when thc spring is unloadccl(shown as the ROLI dashedline). HOMENT (tl{r) Validity of Model

A lull-scaleinstrumcnted rollover test was not fcasible due to resourcelimitations, so thesimulation coulcl not bc checkeddirectly. Howevcr, similar earlier work on the dynamic behaviour of buscs during superstructure strength tests showed reasonablecorrelation betwccn measurementsof actual testsfrorn high-speecicinc film and resultsprcdicted by a 6" of I'rccdommodel(2). Since Rn SP containsmany routinesderived frorn the earlicr modcl, and an energychecksum insures that the total ensrgy variation is minimal, the resultsof RASp are consideredto be of value,particularly for comparingone vehiclewith another.

Data Measurement F,OIATl0X(red) Nine different vehicleswerc testedto determineby Figure 4. Representation of roll stiffness nonlinearities expenment the valucsof the parametersrequired for the

938 ' Section4. Technical.Sesstozs simulation program. Most wereconsidered to be poten- passengers is 2'8"(0.8 l3m), theoverall CG hcightfor the tially significatrtiirctors aliccting rollover periolmance. ladcn vehiclecan be deterurined.

Height of Centre of Gravity Roll Moment of Inertia

The samemethod and equipmentused for determining With the vehicle on the sametest rig as for the CG "'l'he CC heightas describecJin SDC BusRoll Moment height mcasurenrent.and the suspetrsionsand tyres 'Iest ol lnertia Rig"(3)was adoptcd. To summarisethc blr,rckedto effectivcly insure rigid body motion, the tcchnique, the vehicle is positioncd with each axle method of determiningthe roll momcnt ol inertia as supportedfronr a transversesteel bearn that hasa central oLrtlincdin (-1)was used. Figure 7 illustratesthe rollerbcaring, allowing thc bus to roil if unrestrained.By importantfcature, namely, thc air springs.wtrith provide mcasuringthc reaction force ( R in Figurc6) l'ora rangeof a restoringrnomcnt when the busis oscillatedabtrut an roll anglesfrom0o to 3o and plotting a graphof thesetwo axisjoir-ring the two beampivots. f he momentof inertia variables,thc CG height may be calculatedfrotn the about the pivot axis is givenby; equationfor staticequilihrium of montentsabout the T Ip = (2kt2+mgh)( pivot. 2o)' The vertical distancefrom the top of thc beam to the pivot is subtractcdto give the unladenCC heightabove where the ground. Note that the suspensionand tyres are ! = combinedspring stiffness on one beam prcvented from deflecting by suitable use of or .iacks | = distancclrom springto pivot blocks,effectively converting thc businto a rigrdbody. m = total oscillatingmass The bus rollover simulations were conducted for | = hcight of cornbinedCG abovcpivot vehiclesin the ladcncondition defined by currenttilt test T = pcriodof freeoscillation regulations,as this is intendedto be thc w()rstcase situationfor rollover stability.This meansthat 63.5kg The roll moment of inertia of the vehicleabout its per passengcrmusl be addedett thc correctposition lor CC is obtainedusing: each seatedor standing passcnger.plus thc driver. Doublc-deckersonly requirethe driver(and conductor) | = Ir-I"-mhz plus passengerson the upperdeck. Knowing the averagescat hcight on eachdcck and whcre Iu = moment of inertiaof support beams given thc regulation hcight I'or the flCi of standing about pivot

rrruma B slrull. Rr - rY[r*(r*\teJ.o R * -[Hl] [w(r+\)].

froa gmphof R v 0, I Grrdirnt . .|1) !t(i + R-tnlrrcrpt . gg

Figure 6. Method of measurement of vehicle CG position

939 Expeimental S"fety Vehicles

JAcr,3 T0 ELttrrlr^It T.tREFTIIITI LIT Y IHIND trtE niltoDtUtEo (sllttLAl MEIHoD usED t0 (|f FltEsEHt) vtHrcl,E c.G. ELIMIXATEIUf PETSIOT{MoYEMEt|T)

IEAM UT'DER ArR tPRtr{CS EEAM PIVOT rwo AxLtg DEANIHG

Figure7, Generallayout of vehicleon roll moment of inertiarig

The timc for severaloscillations was recor.dcd and the averagecalculated from severalsuch measurernents. This lolr rrfl.E proce$s was repeated for three different air spring A;oN pres$" res.

flttGffflD dt UHtll Stiffnesses It^RtdG utbtt €ICT WHEEL Vertical, lateral,and roll stiffnesseswere obtained for the suspensionand tyres ol'each axle of a vehicleby applying a force in a particulardirection, and measuring both the force and the associateddellection in the same illrEIA PollrtroHEYtIt direction.Vertical force was applied by loadingsandbags ($u 0t EAo{ AtLt to rErsurt wFrtc{. t llEI and was measuredwith weighpads-"onefor eachwhccl, ll0 torr olttlrcrxfllr$) Roll moment wasobtained by shiftingthe sandbags from one side of the bus to the othcr. By calculating the diffcrencebetween weighpad readings and measuringthe distancebetwccn wheels on oneaxle , the actualapplied roll moment wasdetermincd. Gravity suppliedthe lateral ,,,,,^",tr component ol f'orceduring a tilt te$t (Figure 8), which wasrecorded using loadcells to measurethe lbrce between Figure 8. Cutaway view of instrumentation the tyre sidcwall and the tilt table restraint. Linear layout for tilt test bearingsundcl the weighpadsminimised lriction losscs from the lateral force. Ily mounting three transducersin the configuration shownin FigureI and measuringtheir initial positions in space,it waspossible, using geometric relationships, to Roll Centre Heights extract separately the vertical, latclal, and roll dis- placementsof one body relativc to another. Graphs of It was possibleto also calculatcthe positionof the force v displaccmentgive an indication ol' linearity. instantaneousroll centreat cachaxle, using the successive Figure I contairrs typical graphs I'or cach stilfncss position of thc displacemcnttrarrsducers during the roll obtainedat one axle. molnenttest.

940 Section4. Technical.fessions

r'EHlCLt:L0lV- FLOoR C0ACir ExperimentalResults sIrFFil€55 t(rdn^Rtt5

A.{LF qEL^r I VE rO GROIJNO BO0Y eEl-^llv€ rC ^{t,E Table I summarisesthc experimentalresults obtained from testsof nine busesirnd coachcsinto the paratncters ^rll that are typical of threecategories of vehicle. EI\ '_,..|\ i'n1 \ Yl SampleRollover Simulation "l-.'- altilrl |trll'^l ll'l{fF{{t r' 'l'able VEEttTALNFHAV:JF The data from I were used to dctermine the thresholdinrpact velocity (that is, the lateral curb-impact velocity that, it exceeded,would causethc vchicle in questionto roll over) for eachgeneralised vchicle.

Simulation Results

The rollover accident simulation program was run usingthe data for the three typicalcoitch categories give n in l-ahle L By running the simulationwith diflerent x valuesfor the curb impact velocity,it was possibleto i tp ig determinethe thresholdimpact velocityItlr eachvehicle E H,. fr! configurationand thesearc given(along with the max- 7 in Table2. Ir Et. imurnroll irngleattained without overturning)

I .ttari r9 r- lrlfl^L tl4(flrl {rr tttttA olsAcffi{l ParametricStudy '.ArFpaL 6FH^rlOup LAIEF^L BEHAVIOUR rYRt ANrjB00t !IlFFNIss To determinethe factorsthat most aff'ectthe rollover undertaken. The Figure 9. Stiffnessesmeasured at one axle propensity, a parametric study was

Table1 . Experimentaldsta generalisedfor thrsetyplcel Coach configuration$

Low-Floor High-Floor 3-Axle Parameter Coachor Bus TouringCoach 2-Decker

Mass(kg) 13,000 16,000 21,000 CGHeight (m) 1.?5 1.60 1.70 Momentof Inertia(kg.m2) 12,OOO 18.000 26,000 vert stif.(kN/m) springs front 600 600 800 mid 1,800 rear 1,OOO r,000 3,000 tyres front 1,900 1,900 1,900 mid 1,900 rear 3,500 3,500 3,500 RollStif.(kNm,zr) springs front 200 120 200 mid 800 rear 500 500 600 Lat.Stif.(kN/ml sprI ngs front 500 1,300 1,400 mid 400 rear l,OOO 1,400 1,300 tyre$ front 700 700 600 mid 1,000 rear 1,000 1,OOO 1,200 Roll.Ctr. Height (m) front 1,00 o.B0 0.90 rear 1.30 095 0.80 Wheelbase(m) 5.80 5.95 6.30 Axle Wt. F:Bl%) 42:58 36:64 34;66

941 Experimental Safety Ve hicles

Table 2, Roilovgr simurationresurts for three typicatcoach contigurstions

Low-Floor High_Ftoor 3 Parameter ili; Coachor Bus TouringCoach 2_Decker Thresholdlmpact Velocity(m,/s) 3.1b Z.gg Z.9S MaximumRoll. Angle(deg) g8.oo 33.70 Bt.So

magnitudes of the variousparameters (mass, moment of vehicle designerswho wish to improve rollover inertia, stilfnesses,and dimensions)for safety. the Low_Floor The dimensionsand mass_related Bus were taken as properticswould be baselinevalues, Keeping the other unlikely to vary more than 20 percentf:rom the baseline variablesat thesebase levcls, each parameter-ln turn was valuesas shown in Figure 10.Other parameters variedto as$essdirectly its cffecton were the thresholclimprrct examined but found to velocity.The preliminary havelittle influenccon rollover resultsltrr the more significant behaviour. factorsare displayedin Figure 10,which usesa normaliscd Thc stiffnesscswere varied by a factor of.two,hut early horizontal scale,obtained by dividing the parameter in indications reveal only nrinor cffects, queritionby its baselinemagnitude, with the roll stiffnesshaving thc greatesteflbct.

IAIAMf IT15: Applications CG llri6ht of This Research o---o Roll Crntrr l{rirhl

F--a Thc Rollovcr loJl llod^+ o{ lilrl;. AccidcntSirnulation program is currently I- -I Hsr being used to invcstigatebus and coach rollover satety particular, and,in to assessthe suitability ot.UK stability legislationIor morjerncoach designs and patterns. t.+ travel

E TJ Acknowledgments

o The author would like 5.t to thank the Departmentof Transport,l,ondon, for pcrmissionto publish { thrspaper, and the New Zealand governrnentwho I t.t . providcclthe doctorate scholarship. Crantield Impact Centre, and o particularly thc retiring o t)irector,Cuy Tidbury, hasbecn ; !.0 invaluablcin coordinatingand assistingtechnically orr r the cxperimentalphirse, tl References

I. Weir, D.H., ..Analysis et al., of truck and bus handling," Vol. Z, Reporr No. DO.f_FIS-B0l-153, June 1974. 0r 0.r t.0 t.t Ll Openshaw,M., roRHrItsto rrnrurrms G. Tidbury, and D. White,..Simula_ (.!_-.-) " tion ol'dynamicsof a busrollover test, X V Meeting of llus ancl L'oach Figure 10. Results of parametric study Experts, Scientific Society of MechanicalEngineers, Hungary, Septcrnber |9g4. Knight and Tidbury,..'theSD(i (Cranfield)bus roll momcnt of inertia test rig." Conl.ercnceof Bus Experts,Ilungarian ScicntificSociety of Mechirnical Discussion Engineers,Budapcst, 198 l.

It is apparent from Figure l0 that the most critical factor alfccting rollover propcnsityis the CG height. Minirnising this should,therel'ore, be the primary goal of

942