Characteristics of Large-Truck Accidents As Represented in Texas Accident Data at Hsrl
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Characteristics of Large-Truck Accidents as Represented in Texas Accident Data at HSRl John A. Green October 1975 Highway Safety Research lnsti tuteNniversi ty of Michigan The research reported herein was conducted under general research funds contributed by the Motor Vehicle Manufacturers Association. The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the MVMA. TECHNICAL REPORT 5TANDARD TITL t PA:t - ---T-~%n~r,rnt Acccsrton No I -- -1 I Characteristics of Larqe-.Truck Accidents as October 1975 1 ----- I Represented in Texas Accident Data at HSRI. Prrform~n~Orgorjl :aton codc - -- -.- - -- 1 7 Author's / 8. Perlormfng Organi:arlon Rfcort Ns John A. Green 1 UM-HSRI-SA-75-12 i I--------- ~ - 9. Performtng Organ<;T+ r,r. N77... :. .i :1 c IC 10. kork Unt No. i Highway Safety Resafz!.rck Institute I The University of Michigan 11. Contract or Grant NO. Ann Arbor, Plichiljs:: 48:05 13. Type of Report and Per~odCoverci -~- -..- -- - ' 12. SFonsariqg ,\gi.n:y Nore --!3 ,-;c Final Report Motor Vehicle bia.nuf;ic t urers Association 2/75 - 6/75 1 320 ~ewCenter ~..liiciir!:-~ I Detroit, Micl!icr?t~- 482.02 14. Sponsoilng Agency CoJc I --.-..-. ----1---- 1 15. Supplementary Note- i ! I I ~ -- - - - 16 Absfroct HSRI-rn~inta~ner~aata on large-truck accidents were assessed to establish ~i~!;chfl!. s coctain the most useful information, to establish tzh;t tr,c~s- 1.l lr_6 ~110-~7about large-truck accidents, and to develop L t>ct-)r~,?::7~41+-iotjz on means of improving the quality of data collect_irr 9l-1 .a*.re- ~.ruzlc accidents. Police-reported acci- dent data for th2 St3.'ie of Texas were found to be the best available date , IL1-t ti~ryiqoritain several weaknesses, which are discussed. flncrnqs -fincernirlg large-truck accidents are presented in terms c f fe: - ;,-~3 i , 3 IJW~IYr weather, accident configuration, truck type, in,~Arj "rcq~cficyand severity factors. In addition, truck and passcnscr Tar involvements are compared. Recommedations are prese~t~~l c~l11: rll ; $13 :.hci necessity of improving the classif i- cation of tr7-lck l:)nes, che c~il~ctionof vehicle data, and the development of a tr~cKda~~age scale. -- -*-- ---- -- 17. Key fiords Accidents Trucks Unlimited -. .. .. - -- {of I.',S eo:: 1' i 23. 5crur<tyCloss~f, foi ~his 21. NO. of Pages 22, Prtic I I I Unc1assif;sd I unclassified 59 L -- - - -- - - - - ..-.L ---- - Form DOT F 1700.7 ,3 231 CONTENTS 1 . INTRODUCTION ......................................1 2 . SUMMARY OF FINDINGS ...............................3 2.1 ~eficienciesand Problems in the Data ........3 2.2 Characteristics of Large-Truck Accidents .....4 2.3 Comparison of Passenger Car and Truck Involvements .................................5 3 . STRENGTHS AND WEAKNESSES OF THE DATA ..............7 3.1 Strenqths of the Data ........................7 3.2 Weaknesses of the Data .......................9 4 . CHARACTERISTICS OF LARGE-TRUCK ACCIDENTS .........13 4.1 ~emporalFactors ............................15 4.2 Roadway and Weather Conditions ..............18 4.3 Accident Configuration ......................19 4.4 Truck Type ..................................22 4.5 Frequency and Severity of Injuries ..........24 4.6 Occupant Injury .............................25 5 . A COMPARISON OF TRUCK AND PASSENGER CAR INVOLVEMENTS .....................................31 5.1 Temporal Factors ............................33 5.2 Roadway and Weather Conditions ..............40 5.3 Vehicle Defects and Vehicle Damage ..........41 5.4 Driver Factors ..............................44 5.5 Occupant Injury .............................48 6 . RECOMMENDATIONS ..................................51 6.1 Truck-Type Categorization ...................51 6.2 The Collection of Detailed Vehicle Data .....52 6.3 Truck Damage Scale ..........................53 BIBLIOGRAPHY OF' TRUCK-RELATED PUBLICATIONS DONE AT HSRI. 1366.1975 ...................................55 TABLES 1. Truck Type Categories in Police Data.............ll 2. Vehicle Types in the Texas Truck File............l3 3. Definition of Large Trucks in the Texas Truck File .......................................14 4. Percentages of Single and Multiple TU Accidents by Road Classification............ .....19 5. Casualty Rate by Vehicle Mix and Collision Configuration ....................................21 6. Percentages of Truck Types with Fatalities for Single and Multiple TU Collisions............23 7. Percentages of Truck Types with Injuries for Single and Multiple TU Collisions............23 8. Percentage of Single and Multiple Traffic Unit Accidents at Different Accident Severity Levels....... ...........................25 9. Most Serious Injury in an "Other" Traffic Unit Involved in a Multiple Traffic Unit Large-Truck Accident. ............................26 10. Most Serious Injury in a Large Truck Involved in a Multiple Traffic Unit Large- Truck Accident ..............................;..,.28 11. Most Serious Injury in a Large Truck Involved in a Single Traffic Unit Large- Truck Accident ...................................30 12. Passenger Car Categories in the Texas Files..,...31 Vehicle Involvements by Month.............,,..,...37 14. Vehicle Involvements by Day of Week..............38 15. Overinvolvement by Vehicle Defects...............42 16. Overinvolvement by Vehicle Damage Area...........43 17. Vehicle Involvements by TAD Damage Scale.........46 18. Overinvolvement by Most Severe Injury ..,.....,...48 1. INTRODUCTION This reyrrr desrribes an HSRI study designed to assess e..irs-j 117 7.i cidc-nt data pertaining to large-truck accidents, to est-~Slisl~the strengths and weaknesses of the best ~iv~;r,as'~data, to derive whatever significant findings the datz may show about large-truck accidents, and to recommc=+,Cmems of improving data-collection and analysis of 5 c--,-~.truck accidents. The study was con- ducted during ?-.#.irjrr iod February to June, 1975 with general respar-t?-<ipport funds contributed by the Motor Vehicle Manufac:?lrer3 Association. Section 2 c~lnrainsa summary of the study findings. Section 3 3iscusse~~the accident data available con- cerning lars -.-' :< 4;cidents and the reasons why the best availa3;ie ,l i'rLl - -nolice-reported data for the State of Texas-ar? less than ideal Section 4 presents what the data show cta~ztlarge-truck accidents. Section 5 presents wha! the Texas data show about truck accidents as compared with passenger-car accidents. Section 6 contains recon~ze.,r5ati.~ns on means of improving data- collection e5rorts. 2. SUMMARY OF FINDINGS A number of findings have resulted from the des- criptive study of large-truck accidents documented in this report . TfLor~ results are referred to as findings rather than conclusions, emphasizing that the purpose of the stu3y was hroa? Ira concept, aimed at delineating the characteristics of large-truck involvements and their relationships +f> ~~asssnqer-carinvolvements, The findinqs 3r' listed below with section number references, TN~PT~t~~e- are applicable, to indicate where in the report 315 r?:evant data in support of this find- ing may be E~1,1itl, 2.1 Deficiencies- and Problems in the Data A) A. rr\aj,a?: finding of this study is that the cate- gorizatior* of trcr4s (11 thc mass data files is generally poor. In the HSXi xcident files, only data from the states of Texas and 'flzshincton use a categorization scheme of any sophi? ticatioi~whatever (Section 3.2) . B) In the Texas Truck File, the majority of trucks with smi-tr.ai;crs wre of unidentified type (Table 2). Thus, the catc<y.,rizatian problem discussed above (i.e. , Section 2.1, pa-t 1,) is worse for semi-trailer trucks than for stla;qhL truzks. This is troublesome, since these unldenA:if;.ed tykes al:caun-c for more than a third of the truck invoi.~emsntsrecorded in the file. C) The szcurrence of large-truck accidents is a relatively rare event, so that very large data samples are required to obtain meaningful statistics. For exam- ple, data froni the state of Texas show 33,000 large- truck involveinents out of 460,000 accidents: a rate of one invclvement for nearly 14 accidents. D) The perceiitage of missincj data for the TAD vehicle darnaye scale, developed by the National Safety Council's Trafftc Accident Data Project, is over twice as large for t:-11cks as i-c is Ecr passenger cars (Section 5.3). This statistic highlights the difficul- ties involved ir! appl.ying a common scale to passenger cars and to 2 wide variety of trucks with considerable structural. vciriatiorzs. E) ~clice-reportedoccupant injury information is generally completely recorded only for accidents involving fata' i-njuries. The less severe the occupant injuries in 3 given accident., the more likely it is that occupant .~.;ury snf ormation will be lost. 2.2 Characteristics ef Larqe-Truck Accidents A) M~Itly;li> t-:ra_'fir:-l;nji- aczidents tend to occur during the recvlar 40-,?(our work vveek while single- traffic unit accidents are more heavily represented at other times (Secti:in 4,1!. This finding is most proba- bly a reflection of the much higher traffic densities which occur eL1lrlncj the day. B) Sjngle traf fic-unit accidents are somewhat more likely to occur under less ideal driving condi- tions than those typical of vultiple vehicle accidents. (Section 4,2). Th~tis, a mailer percentage of sin- gle traffic-unit accidents occur in clear weather on dry roads in good condition. C) In multiple traffic-unit accidents, the casualty rate (i.e,, number killed or injured per acci- dent) for all colllsioli