US. Depart menf of Transportation National Highway Traffic Safety Administration DOT HS 807 489 November 1989 NHTSA Technical Report An Evaluation of Door Locks and Roof Crush Resistance of Passenger Cars- Federal Motor Vehicle Safety Standards 206 and 216 This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161. The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear only because they are considered essential to the object of this report. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. DOT HS 807 489 4. Title and Subtitle 5. Report Dote AN EVALUATION OF DOOR LOCKS AND ROOF CRUSH November 1989 RESISTANCE OF PASSENGER CARS - Federal Motor 6. Performing Orgonuation Code Vehicle Safety Standards 206 and 216 8' Performing Organization Report No. 7. Author's) Charles 0. Kahane, Ph.D. 9. Performing Organization Nam* and Address 10. Work Un.t No. (TRAIS) Office of Standards Evaluation National Highway Traffic Safety Administration 11. Controct or Gront No. Washington, D.C. 20590 13. Type of Report ond Period Covered 12. Sponsoring Agency Nome and Address Department of Transportation NHTSA Technical Report National Highway Traffic Safety Administration Washington, D.C. 20590 14. Sponsoring Agency Code 15. Supplementary Notes An agency staff review of existing Federal regulations performed in response to Executive Order 12291. 16. Abstract Federal Motor Vehicle Safety Standard 206 - Door Locks and Door Retention Compo- nents - is aimed at reducing the likelihood of occupant ejection in crashes. The industry steadily improved door lock design during the 1960's. Standard 216 - Roof Crush Resistance - is designed to reduce deaths and injuries due to the crushing of the roof into the passenger compartment in rollover crashes. Hardtops were redesigned as pillared cars, with stronger roof support. This evaluation analyzes the effectiveness and benefits of stronger door locks and roof structures in rollover crashes of passenger cars. It also estimates the cumulative effect on fatality risk - for unrestrained occupants in rollover crashes - of all safety standards and vehicle modifications of the 1963-82 era. The study is based on statistical analyses of FARS, Texas, NCSS, NASS and MDAI data and roof crush tests on pre- and post-Standard 216 cars. It was found that: o Door latch improvements implemented during 1963-68 save an estimated 400 lives per year, reducing the risk of ejection in rollover crashes by 15 percent. o The shift from hardtops to pillared cars, in response to Standard 216, saves an estimated 110 lives per year. 17. Key Word* 18. Distribution Statement rollover; ejection; door lock; latch; Document is available to the public hinge; B pillar; hardtop; Volkswagen; through the National Technical crashworthiness; crash avoidance; FARS; Information Service, accident analysis; stability; Texas; Springfield, Virginia 22161 statistical analysis; NASS; NCSS; MDAI; 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. Ns. of Poges 22. Price Unclassified Unclassified 283 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized TABLE OF CONTENTS Summary xiii 1. INTRODUCTION AND BACKGROUND 1 1.1 Evaluation of NHTSA regulations and programs 1 1.2 Standard 206 - Door Locks and Door Retention Components 2 1.3 Standard 216 - Roof Crush Resistance 4 1.4 Background 8 1.5 Other vehicle modifications that affected rollover risk 12 1.6 Current NHTSA activities 15 2. EARLIER STUDIES OF ROLLOVER PROPENSITY AND FATALITY RISK 19 2.1 Car size and rollover propensity 19 2.2 Other factors which affect rollover propensity 25 2.3 Effect of door lock improvements 27 2.4 Relative risk of ejected and nonejected occupants 30 2.5 Effect of roof crush strength 32 2.6 Descriptive studies of rollovers 36 3. ROOF CRUSH STRENGTH BY MODEL YEAR, BASED ON LABORATORY TESTS 39 3.1 Compliance tests for Standard 216 39 3.2 Additional tests of older cars 43 3.3 Data elements for the statistical analysis 47 3.4 Ranking the cars on crush performance 49 3.5 Comparison of old and new cars 53 3.6 A simple model: no adjustment for market class or manufacturer..55 3.7 A model which adjusts for market class and manufacturer 62 iii 4. ROOF CRUSH STRENGTH BY MODEL YEAR, BASED ON ROLLOVER CRASHES 71 4.1 Data preparation 72 4.2 Biases due to data source and vehicle size 75 4.3 A model which adjusts for data source and vehicle size 79 5. ROLLOVER PROPENSITY BY MODEL YEAR: ANALYSES OF TEXAS DATA .87 5.1 Analysis objectives and approach 87 5.2 Data preparation, key variables and calendar year correction....93 5.3 A simple model: no control for vehicle size and weight 101 5.4 Rollover propensity by market class ....104 5.5 A model which adjusts for vehicle size and weight 109 5.6 Rollover propensity indices 119 6. ROLLOVER FATALITY RISK BY MODEL YEAR: ANALYSES OF FARS DATA 126 6.1 Analysis objectives and approach 127 6.2 Data preparation, key variables and calendar year correction...130 6.3 Simple models: no control for vehicle factors 140 6.4 Rollover fatality risk by market class 142 6.5 Models of rollover ejection risk 149 6.6 Models of rollover nonejection risk ...159 7. ANOTHER APPROACH TO STUDYING OCCUPANT PROTECTION IN ROLLOVERS 169 7.1 Analysis objectives and approach 170 7.2 Measuring and maximizing "scrambling" of the market classes....176 7.3 Crashworthiness trend lines ...188 7.4 Rollover crashworthiness indices 197 iv 8. THE NET EFFECT OF VEHICLE MODIFICATIONS ON ROLLOVER FATALITIES 205 8.1 Analysis objectives 205 8.2 Calculation of baseline fatalities 206 8.3 Combined effect of all vehicle modifications, 1963-82 209 8.4 Fatality distribution within a model year, by market class 210 8.5 Estimated effects of vehicle modifications 214 References 229 Appendix A: Compliance test results for Standard 216 237 Appendix B: Sizes and weights of cars, by make/model and model year 243 LIST OF TABLES Table 3-1 Test results: roof crush resistance of used cars 46 3-2 Roof crush of 128 cars at force level required by Standard 216 50 3-3 Roof crush of 128 cars at force level 10 percent over Standard 216 specification 51 3-4 Combined normalized roof crush score for 128 cars 52 8-1 FARS 1975-86: reported fatalities in primary rollovers, by calendar year, passenger cars 208 8-2 Percent of fatalities in each market class, by model year and type of fatality 212 8-3 Estimated rollover fatalities in each market class, by model year 215 8-4 Annual effect of vehicle modifications on fatalities in rollover crashes 216 LIST OF FIGURES Figure 3-1 Scattergram of CRUSH3 (unadjusted crush score) by model year 56 3-2 Average value of CRUSH3 (unadjusted crush score) by model year (grouped) 57 3-3 Scattergram of CRUSH3 (unadjusted crush score) by model year and body style 60 3-4 Average value of CRUSH3 (unadjusted crush score) by model year (grouped) and market class 61 3-5 Scattergram of CRUSH4 (adjusted crush score) by model year 64 3-6 Scattergram of CRUSH4 (adjusted crush score) by model year and body style 66 3-7 Average value of CRUSH4 (adjusted crush score) by model year (grouped) and market class 67 3-8 Average value of CRUSH4 (adjusted crush score) by model year (grouped) 68 4-1 Average roof deformation extent zone by model year and data source 76 4-2 Average roof deformation extent zone by model year and market class - observed, unadjusted data 78 4-3 Average roof deformation extent zone by model year and market class - adjusted for data source and car size 82 4-4 Average roof deformation extent zone by model year and body type 83 4-5 Average roof deformation extent zone by model year - adjusted for data source and car size 85 5-1 Reported log odds ratio of rollovers to frontal fixed object impacts, by model year and calendar year 95 5-2A Log odds ratio of rollovers to frontal fixed object impacts, by model year (calendar year correction including vehicle age term) 102 vii 5-2B Log odds ratio of rollovers to frontal fixed object impacts, by model year (calendar year correction excluding vehicle age term) 103 5-3A Rollover propensity by model year and market class (calendar year correction term including vehicle age term) 106 5-3B Rollover propensity by model year and market class (calendar year correction term excluding vehicle age term) 107 5-4A Rollover propensity, adjusted for car size and weight, by model year and market class (calendar year correction term including vehicle age term) 114 5-4B Rollover propensity, adjusted for car si2e and weight, by model year and market class (calendar year correction term excluding vehicle age term) 115 5-5A Rollover propensity, adjusted for car size and weight, by model year and market class, drawn to the same scale as the unadjusted data (calendar year correction term including vehicle age term) 116 5-5B Rollover propensity, adjusted for car size and weight, by model year and market class, drawn to the same scale as the unadjusted data (calendar year correction term excluding vehicle age term) 117 5-6A Rollover propensity, adjusted for car size and weight, by model year (calendar year correction term including vehicle age term) 120 5-6B Rollover propensity, adjusted for car size and weight, by model year (calendar year correction term excluding vehicle age term) 121 5-7A Adjusted (plain line) and unadjusted (hatched line) rollover propensity indices (calendar year correction including vehicle age term) 124 5-7B Adjusted (plain line) and unadjusted