An Evaluation of Side Structure Improvements in Response to Federal Motor Vehicle Safety
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November 1982 DOT HS 806 314 NHTSA Technical Report An Evaluation of Side Structure Improvements in Response to U.S'Department of Transportation Federal Motor Vehicle Safety National Highway Traffic Safety Administration Plans and Programs Office of Program Evaluation \ l'^ This document is available to the U.S. public through the National Technical Information Service, Springfield, Virginia 22161 Technical Report Documentation Page 1. Report N 1. 2 Gtn i i o n No. 3. Recipient's Catalog No. DOT HS 806 314 •1, Titl® o'nri Subtitle 5. Report Date An Evaluation of Side Structure Improvementp s _ Novemhc:r..l98?. J RResponse to Federal Motor Vehicle Safety Standard 6. Performing Organisation Code 214 NPP-10 8. Performing Organization R«port No. 7. Author's) " " " ~' ~ " "" "~ Char_les_ Jesse Kahane, Ph.D. 9. Performing Orgoni notion Name and Address 10. Work Unit No. (TRAIS) Office of Program Evaluation National Highway Traffic Safety Administration i 1. Contract or Grant No. 400 7th Street, S.W. n ^. C. 205 90 13. Type of Report ond Period Covered 12, Sponsoring Agency Nome and Address NHTSA Technical Report U.S. Department of Transportation National Highway Traffic Safety Administration Washington, D.C. 20590 4, Sponsoring Agency Code 15. Suppl«mentary Notes An Agency staff review of an existing Federal regulation performed in response to Executive Order 12291. 16. Abstract "" Side door beams were installed in passenger cars in response to Federal Motor Vehicle Safety Standard 214. The purpose of beams is to reduce the velocity and depth of door intrusion into the passenger compartment in side impact crashes. The objectives of this Agency staff evaluation are to determine how many fatalities and injuries are prevented by Standard 214, to measure the actual cost of the standard, to assess cost effectiveness and to describe the actual crash performance of equipment Installed in response to the standard. The evaluation is based on statistical analyses of the Fatal Accident Reporting System and National Crash Severity Study data, cost analyses of production beam assemblies and a review of staged crash tests. It was found that o Standard 214 elimin!!i<%,*$*30 fatalities and 4,500 nonfatal hospitall- zations per year in side impacts with fixed objects. The standard has brought about significantly shallower and wider damage patterns and has reduced occupant ejection in these crashes. o Standard 214 eliminates 4900 nonfatal hospitalizations per year in vehicle-to-vehicle side impacts but has not reduced fatalities in these crashes. Door intrusion was significantly reduced. o Standard 214 has added $61 (in 1982 dollars) to the lifetime cost of owning and operating a car. 17. Key Words 18. Distribution Statement %i} side door beam; side impact; angle Document is available to the public collision; Federal Motor Vehicle. Safety through the National Technical Information Standard 214; accident analysis; Service, Springfield, Virginia 22161 evaluation; statistical analysis; cost effectiveness 19. Security Clo&sif. (of this r«port) 20. Security Clo»sif. (of this pogo) 21. No. of Pages 22. Price Unclassified Unclassified 430 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized METRIC CONVERSION FACTORS A»»m!aata CranniMis t* Mttrie Mtiiaru Asprtiimit* C*a«irsj*ci Iita UsUit Mtasttts T» KM* Msftwh .7 T> farf Wkta Tw XMW T. 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Ccleiua Kr^a^. KM 32) 5/9 {ahar "C •F 32) °F 96.3 -40 O |40 80 I . ISO ISO ZOO 1 1 • • • 1 r ' • • • i«iii 1 d 1—" 1 1 1 T^ 1 1 nr r^ 1 -40 -K) 6 1 *Or r 1*f<0 • SO 10 IOD -= = E •c ST •c TABLE OF CONTENTS Acknowl edgroents Executive Summary 1. INTRODUCTION 1 1.1 Federal Motor Vehicle Safety Standards - the program and its evaluat ion „ 1 1.2 What is Standard 214? . ... 4 1.3 Why reevaluate Standard 214? 5 1.4 Contents of the evaluation. 6 2. FINDINGS AND CONCLUSIONS. , 9 2.1 Principal statistical findings 9 2.2 The side impact safety problem. 16 2.3 Effectiveness of Standard 214 21 2.3.1 Fatality reduction 22 2.3.2 Serious injury reduction 25 2.3.3 Nonscrious injury reduction.. 33 2.4 Why is Standard 214 effective? , 33 2.4.1 Five hypothesef-'wi, effectiveness 33 2.4.2 Effect of StandarcfHH.4 on vehicle damage patterns 36 2.4.3 Effect of Standard 214 on specific types of injuries 44 2.4.4 Summary 48 2.5 Costs, benefits and cost-effectiveness.... 50 2.6 Comparison with NHTSA's 1979 preliminary evaluation 52 2.7 Strengths and weaknesses of the evaluation 56 2.8 Conclusions. 57 iii ', THE SIDF IMPACT SAFETY PR HiLEM fix 3.1 The number and severity of casualties in side impacts.... 61 (.1.1 Fat: a 1 11. i es 61 ).l, 2 HospIt.a 1 i zat ions 64 J.I. i AIS dist ribution ;. 68 3.2 Injury iiiechani sm.s and contributing factors - a literature review., 70 ). 2 . 1 Injury mechanisms 70 3.2.2 ('out r J but i up factors - i 74 3.) Statistical assessment of injury mechanisms I 75 1.3.1 Contact sources ol serious injuries 1 75 3.3.2 Body region and contact source of serious injuries......... 78 '(.3.3 Boiiv region and contact source of fatal and life-threating i n j u r i o.s , 80 3.4 .S tat. i ,-.t i c.i 1 an-ilv'.is of factors contributing to injury risk....... 83 3.4.1 Number al vehicles in the aceIdent,occupant location and itnpac I sire 81 3 . 4. ,' Do ]. t a V 85 3. 4 . 3 Crush d^pt h 87 3.4.4 Sill override in multivehicle crashes '• 92 3.4.5 Type of object or vehicle contacted...... 92 4. STANDARD 214 AND OTHER IMPROVEMENTS TN SIDE IMPACT PROTECTION 99 4.1 Elements of the side structure.. 99 4 . 2 Development and imp] ementat ion of Standard 214 100 4.2.1 Developments that, preceded regulation 100 4 .2.2 Repularory history 102 4.2.3 Vehicle modifications in response to Standard 214 .106 4.2.4 Imp] ementat ion schedule .107 4.) Discussion: whv might Standard 214 be effective? ....109 4.3.1 Five hypotheses on effectiveness .109 4.3.2 Review of crash test results .115 4.4 Side structure modifications other than Standard 2.14 .......117 4.4.1 Other safety standards- .119 4.4.2 Vehicle modifications not mandated by safety standards ..121 4.4.3 Chronology of side structure modifications and res ty ling 122 4.4.4 Some current research concepts in side impact protect ten...{26 IV 5. REVIEW OF PREVIOUS STATISTICAL STUDIES OF STANDARD 214 131 5.1 Preston & Shortridge (1973) - Denver, MDAI and Texas data 131 5.2 Joksch (1973) -- Texas data 133 5.3 McLean (1974) - North Carolina data 133 5.4 Jones (1977) - Calspan data....... 135 5.5 Kahane (1979) - NCSS data 136 5.6 Cameron (1980) - Victoria insurance claims .139 5.7 Chi (1980) - NCSS data 139 6. FATALITY REDUCTION FOR STANDARD 214: ANALYSES OF FARS DATA 143 6.1 Analysis methods. 144 6. 2 Data preparation 148 6.3 Analyses of side/frontal contingency tables 151 6.3.1 First year with beams vs. last year without them ...151 6.3.2 First two years with beams vs. last two years without them. 154 6.3.3 Confidence bounds for the fatality reduction in single vehicle crashes 158 6.4 Regressions of the proportions of side and frontal fatalities. .161 6.5 Side impact fatalities per 1000 vehicle years 167 6.6 Regressions of side impact fatality rates per 1000 vehicle years 174 6. 7 Summary of results 179 SERIOUS INJURY REDUCTION !•'(')K STANDARD 214: ANALYSES OF NCSS 7.1 NCSS overview, definitions and analysis methods . ..184 7.1.1 Definition of side impact and nearside/compartment impact 185 7.1.2 Definition of pre and post - Standard 214 186 7.1.3 Definition of. injury , . 187 7.1.4 Preview of analysis methods 187 7.2 The analyst's dilemma: sample size vs. freedom from bias....... 194' 7.3 Preliminary effectiveness estimates - based on tabulations of the raw data 198 7.4 Sources of bias in the preliminary estimates 204, 7.4.1 Safety standards other than Standard 214 2041 l.h.2 Vehicle modifications not mandated by safety standards 207 7.4.3 Vehicle age biases that can be removed by control variables 210 7.4.4 Some invalid control variables 211' 7.4.5 Other vehicle age-related biases 214 7.4.6 Towaway criterion biases that can be removed by control variables 219 7.4.7 Towaway criterion biases due to Standard 214 itself 221 7.5 Refined effectiveness estimates - based on multidimensional contingency table analyses 225 7.5.1 Procedure 225 7.5.2 Definitions of the control variables 228 7.5.3 Effectiveness in single vehicle crashes , 232 7.5.4 Effectiveness in tnultivehicle crashes 238 7.5.5 Effectiveness for nearside occupants in multi.vehicle compartment; crashes 246 7.6 A caveat - injury "reductions" in frontal crashes 253 7.7 Life-threatening injury reduction 258 7.8 Summary: "best" estimates of Standard 214 effectiveness 262 vL 8.