Federal Motor Vehicle Safety Standard No. 121 mandates antilock braking systems (ABS) on all new airbraked 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 percent. This is based on data from seven States and controls for the age of the tractor at the time of the crash. This represents a statistically significant 6-percent 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-percent reduction in crash involvement, resulting from a 4-percent 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 jack-knives, off-road overturns, and at-fault involvements in collisions with other vehicles (except front-to-rear collisions). Counteracting are 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. (Author/publisher)
Samenvatting