Numerous crash data statistical analyses conducted over the past few years suggest that, for automobiles, the introduction of four-wheel antilock brake systems (ABS) has produced net safety benefits much lower than originally expected. The studies indicate the apparent increase in single-vehicle crashes involving passenger cars equipped with four-wheel ABS almost completely offsets the safety advantage such vehicles have over their conventionally-braked counterparts. Other studies have suggested that this may be occurring because people drive faster in ABS-equipped vehicles, such as due to behavioral adaptation. As part of its Light Vehicle ABS Research Program, NHTSA conducted an observational experiment to investigate the possibility of behavioral adaptation resulting from ABS. An experiment was conducted to unobtrusively determine whether drivers of vehicles equipped with ABS have a tendency to drive faster than drivers of conventionally braked vehicles. Several locations on public roadways around Ohio were selected as data collection sites. At these sites, the speed and license plate information of passing vehicles were unobtrusively measured and recorded using a laser speed gun, video camera, and laptop computer. Data were collected at each site for specified periods during daylight hours (balanced for AM/PM) in both wet and dry road conditions. Using the license plate number, the VIN number was obtained and then decoded to determine whether each vehicle had ABS. Average speed data for specified conditions and locations were compared for vehicles with ABS versus those without. The results of this study showed that type of brake system (ABS or conventional) had no significant effect on driving speed under the conditions examined. This finding of no significant speed effects was true for all sites, pavement conditions, and model years of vehicles observed. A consistent, but insignificant, trend was seen in mean speed by brake system for each site where higher speeds were observed for drivers of ABS-equipped vehicles. Significant results that were found included higher speeds for drivers of newer model cars, higher speeds for dry pavement, and that speed as a function of location (site). Overall, based on observed vehicle speed results, evidence of passenger car ABS-related driver behavioral adaptation was not observed using the methods employed in this study. Based on these and other related results from NHTSA’s Light Vehicle ABS Research Program, the authors believe that behavioral adaptation due to ABS is not occurring during 'real world' driving. Thus, the results of this study suggest that the apparent increase in single-vehicle crashes involving ABS-equipped vehicles cannot be attributed to behavioral adaptation. (Author/publisher)
NHTSA Light Vehicle Antilock Brake System Research Program Task 7.1 : examination of ABS-related driver behavioral adaptation : license plate study.
20210737 ST [electronic version only]
Washington, D.C., U.S. Department of Transportation DOT, National Highway Traffic Safety Administration NHTSA, 2001, VII + 24 p., 13 ref. DOT HS 809 430