DOT HS 811 182 August 2009 The Long-Term Effect of ABS in Passenger Cars and LTVs This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161 This publication is distributed by the U.S. Department of Transportation, National Highway Traffic Safety Administration, in the interest of information exchange. The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Department of Transportation or the National Highway Traffic Safety Administration. The United States Government assumes no liability for its content or use thereof. If trade or manufacturers’ names or products are mentioned, it is because they are considered essential to the object of the publication and should not be construed as an endorsement. The United States Government does not endorse products or manufacturers. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. DOT HS 811 182 4. Title and Subtitle 5. Report Date August 2009 The Long-Term Effect of ABS in Passenger Cars and LTVs 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Charles J. Kahane and Jennifer N. Dang 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Evaluation Division; National Center for Statistics and Analysis National Highway Traffic Safety Administration 11. Contract or Grant No. Washington, DC 20590 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered National Highway Traffic Safety Administration NHTSA Technical Report 1200 New Jersey Avenue SE. 14. Sponsoring Agency Code Washington, DC 20590 15. Supplementary Notes 16. Abstract Statistical analyses based on data for calendar years 1995 to 2007 from the Fatality Analysis Reporting System (FARS) and the General Estimates System (GES) of the National Automotive Sampling System (NASS) estimate the long-term effectiveness of antilock brake systems (ABS) for passenger cars and LTVs (light trucks and vans) subsequent to the 1995 launch of public information programs on how to use ABS correctly. ABS has close to a zero net effect on fatal crash involvements. Fatal run-off-road crashes of passenger cars increased by a statistically significant 9 percent (90% confidence bounds: 3% to 15% increase), offset by a significant 13-percent reduction in fatal collisions with pedestrians (confidence bounds: 5% to 20%) and a significant 12-percent reduction in collisions with other vehicles on wet roads (confidence bounds: 3% to 20%). ABS is quite effective in nonfatal crashes, reducing the overall crash- involvement rate by 6 percent in passenger cars (confidence bounds: 4% to 8%) and by 8 percent in LTVs (confidence bounds: 3% to 11%). The combination of electronic stability control (ESC) and ABS will prevent a large proportion of fatal and nonfatal crashes. 17. Key Words 18. Distribution Statement NHTSA; FARS; NASS; GES; FMVSS; crash- This report is free of charge from the NHTSA Web avoidance; effectiveness; fatality reduction; lives site at www.nhtsa.dot.gov saved; brakes; statistical analysis; benefits 19. Security Classif. (Of this report) 20. Security Classif. (Of this page) 21. No. of Pages 22. Price Unclassified Unclassified 89 Form DOT F 1700.7 (8-72) i TABLE OF CONTENTS List of abbreviations ....................................................................................................................iv Executive summary......................................................................................................................vi 1. History of ABS and previous effectiveness findings........................................................... 1 1.1 Rationale for ABS....................................................................................................... 1 1.2 Stopping test findings ................................................................................................. 2 1.3 Market and regulatory history..................................................................................... 5 1.4 Initial effectiveness analyses....................................................................................... 7 1.5 The safety community’s response............................................................................. 10 1.6 The second generation of effectiveness analyses...................................................... 12 1.7 Developments since 2002 ......................................................................................... 14 1.8 Goals of the evaluation ............................................................................................. 15 2. Effect of ABS in fatal crashes: analyses of 1995-2007 FARS data................................... 17 2.0 Summary................................................................................................................... 17 2.1 Analysis for passenger cars....................................................................................... 17 2.1.1 FARS calendar year range .............................................................................. 17 2.1.2 Control group involvements versus response group....................................... 17 2.1.3 Cars without ABS versus cars with ABS........................................................ 19 2.1.4 Adjusting the case counts for air bag effectiveness........................................ 22 2.1.5 Results............................................................................................................. 24 2.1.6 Comparative results for four cohorts of cars................................................... 28 2.1.7 Drinking versus non-drinking drivers............................................................. 30 2.1.8 Net effect by specific road-surface condition ................................................. 33 2.2 Analysis of rear-wheel ABS for LTVs ..................................................................... 33 2.2.1 LTVs without ABS versus LTVs with rear-wheel ABS................................. 33 2.2.2 Results............................................................................................................. 36 2.3 Analysis of four-wheel ABS for LTVs..................................................................... 39 2.3.1 LTVs with rear-wheel ABS versus LTVs with four-wheel ABS ................... 39 2.3.2 Results............................................................................................................. 41 2.3.3 Drinking versus non-drinking drivers............................................................. 45 ii 3. Effect of ABS in all crashes: analyses of 1995-2007 GES data ........................................ 47 3.0 Summary................................................................................................................... 47 3.1 Analysis for passenger cars....................................................................................... 47 3.1.1 GES calendar year range................................................................................. 47 3.1.2 Control group involvements versus response group....................................... 48 3.1.3 Cars without ABS versus cars with ABS........................................................ 49 3.1.4 Results............................................................................................................. 50 3.1.5 Comparative results for four cohorts of cars................................................... 55 3.1.6 Net effect by specific road-surface condition ................................................. 56 3.1.7 Net effect on injury crashes ............................................................................ 56 3.2 Analysis of rear-wheel ABS for LTVs ..................................................................... 57 3.2.1 Results............................................................................................................. 57 3.3 Analysis of four-wheel ABS for LTVs..................................................................... 60 3.3.1 Results............................................................................................................. 61 4. Discussion.......................................................................................................................... 66 4.1 Summary and comparison of effectiveness estimates .............................................. 66 4.2 Why is the effect still negative in run-off-road crashes? .......................................... 68 4.3 Combined effect of four-wheel ABS and ESC......................................................... 69 4.4 Long-term benefits and costs of four-wheel ABS .................................................... 71 References................................................................................................................................... 74 iii LIST OF ABBREVIATIONS ABS Antilock brake system AIS Abbreviated Injury Scale ANPRM Advance Notice of Proposed Rulemaking BAC Blood alcohol concentration, measured in grams per deciliter (g/dL) BMW Bayerische Motoren Werke CY Calendar Year df Degrees of Freedom DOT United States Department of Transportation ESC Electronic Stability Control FARS Fatality Analysis Reporting System, a census of fatal crashes in the United States since 1975 FMVSS Federal Motor Vehicle Safety Standard GDP Gross Domestic Product GES General Estimates System of NASS GM General Motors GVWR Gross vehicle