Background Initial studies of existing Antilock Brake Systems (ABS) for light trucks (1993) and passenger cars (1995) did not show a significant overall fatality reduction. Benefits for multivehicle crashes on wet roads and for pedestrian crashes were offset by increases in run-off-road crashes including rollovers. Extensive research by NHTSA and others never really explained the observed increase in run-off-road crashes (although one study hinted at a combination of impaired driving and inexperience with ABS). Subsequent crash analyses (1998-2001) suggest these negative effects may have waned, but still didn't show a significant net fatality reduction. ABS is due for a follow-up evaluation, because the public has received extensive information about how to use ABS, and many years of on-the-road experience with the systems. The design of ABS may also have changed over the years.

Objectives Determine the effect of ABS, if any, on fatal and non-fatal crashes, by crash type, vehicle type and model year, vehicle age, driver characteristics, and roadway/environmental characteristics. Track the effect of ABS on run-off-road crashes over time. Identify groups of drivers, if any, that currently experience significant reductions in crashes or fatalities with ABS.

Proposed Approach Statistical analyses of the effectiveness of FARS and State crash data files and registration data: crash involvement rates will be compared for recent-ABS, early-ABS and non-ABS vehicles, for various types of crashes where ABS might have an effect relative to a control group of crash involvements that do not involve braking, or on a per-vehicle-year basis. The analyses will emphasize identifying those populations that experienced an increase in run-off-road crashes, and conversely those populations that significantly reduced crashes with ABS. The evaluation, based on existing data, may take 1-2 years.