A new technical report is now available from the National Highway Traffic Safety Administration (NHTSA) assessing antilock braking performance on heavy-duty trucks and trailers. The report provides a performance review of the systems required under NHTSA's current Safety Standard 121, Air Brake Systems. The report's title is: The Effectiveness of ABS [Antilock Braking Systems] in Heavy Truck Tractors and Trailers.
FMVSS 121 (49 CFR 571.121) mandated antilock braking systems (ABS) on all new air-braked vehicles with a GVWR of 10,000 pounds or greater. ABS is required on tractors manufactured on or after March 1, 1997, and air-braked semi-trailers and single-unit trucks manufactured on or after March 1, 1998.
The primary findings of this report are the following:
The best estimate of a reduction by ABS on the tractor unit in all levels of police-reported crashes for air-braked tractor-trailers is 3%. This is based on data from seven states and controls for the age of the tractor at the time of the crash. According to NHTSA officials, this represents a statistically significant 6% reduction in the crashes where ABS is assumed to be potentially influential, relative to a control group, of about the same number of crashes, where ABS is likely to be irrelevant.
In fatal crashes, there is a non-significant 2% reduction in crash involvement, resulting from a 4% reduction in crashes where ABS should be potentially influential. The age of the tractor at the time of the crash is not important. Rather, external factors of urbanization, road speed, and ambient lighting are influential and are accounted for in the final estimate.
Among the types of crashes that ABS influences, there is large reduction in jackknives, off-road over-turns, and at-fault involvements in collisions with other vehicles (except front-to-rear collisions). Counteracting were an increase in the number of involvements of hitting animals, pedestrians, or bicycles and, only in fatal crashes, rear-ending lead vehicles in two-vehicle crashes.
The technical report is available on the Internet for viewing in PDF format at http://www-nrd.nhtsa.dot.gov/Pubs/811339.pdf. A copy of the report can be obtained free of charge by sending a self-addressed mailing label to Charles J Kahane (NVS-431), National Highway Traffic Safety Administration, Room W53-312, 1200 New Jersey Ave, SE, Washington DC 20590.
Comments on the report can submitted to NHTSA [identified by Docket Number NHTSA-2010-0116] online at http://www.regulations.gov. Follow the online instructions for submitting comments, which must be received by December 20, 2010.