Background In 1996, NHTSA amended FMVSS 105 (hydraulic brake system) and FMVSS 121 (air brake system) to require ABS and a malfunction indicator lamp (MIL lamp) on all new heavy vehicles (GVWR greater than 10,000 pounds). Implementation was performed over a three-year period: air-brake truck tractors manufactured on or after March 1, 1997, air-brake trailers and single-unit trucks manufactured on or after March 1, 1998, and hydraulic braked trucks manufactured on or after March 1, 1999. The purpose of ABS is to help maintain directional stability and control during braking and possibly reduce stopping distances on some road surfaces, especially on wet roads. ABS may prevent crashes involving loss of control, skidding, jackknife, and possibly trucks with conventional brakes unable to stop in time to avoid hitting another vehicle.
Objectives Estimate the effect of ABS on truck tractors and trailers involved in single-vehicle and multi-vehicle crashes (especially crashes involving loss of control, skidding, or jackknife) by road surface condition. Estimate the cost per vehicle for the initial installation and subsequent maintenance of ABS and its related control and malfunction warning systems. Examine the durability and reliability of ABS.
Proposed Approach NHTSA plans to collect medium and heavy truck crash data from one or more large State police agencies for a period of 2-3 years. Every crash involving a tractor-trailer, a bobtail tractor, or a medium or heavy single-unit truck will be investigated and data sent to NHTSA. Statistical analyses of the effectiveness of the new medium/heavy duty truck anti-lock brake standard will be assessed using the State police accident reports and NHTSA supplemental crash report forms, along with FARS and State crash data files. Crash involvement rates will be compared for ABS and non-ABS vehicles, for various types of crashes where ABS is likely to be effective (loss-of-control, skidding, jackknife, multi-vehicle) vs. a control group of crash involvements that do not involve braking. In addition, information about what vehicles have ABS will be obtained from truck and trailer manufacturers. The cost for the initial installation of ABS will be estimated from "teardown" analyses or from information provided by manufacturers. Maintenance costs, durability, and reliability of the ABS will be studied in government and/or private trucking fleets.
Status. Collection of crash data will begin in 2004 with the North Carolina State Highway Patrol and will continue until late 2005. Statistical analyses will begin in 2006. The survey of maintenance costs, durability, and reliability of ABS is underway. The teardown analysis has been completed.