Background NHTSA issued FMVSS 223 and 224 in January 1996 to reduce the number of deaths and serious injuries that occur when light duty vehicles collide with the rear end of trailers and semi-trailers. FMVSS 223 specifies the height, width, length, and strength requirements for rear impact guards for trailers and semi-trailers; whereas, FMVSS 224 establishes requirements for the installation of rear impact guard on trailers and semi-trailers with a GVWR of 10,000 pounds or more manufactured on or after January 1998. However, the Truck Trailer Manufacturers Association (TTMA) had already issued a voluntary Recommended Practice in April 1994 that included all the essential elements of the subsequent NHTSA standards except for the energy absorption requirement. Between January 1952 and 1998, trailers and semi-trailers were Federally regulated by Federal Motor Carrier Safety Regulations (FMSCR) or their predecessors that mandated rear impact guards, which allowed substantially smaller guards than the NHTSA standard and the TTMA recommended practice and imposed no strength tests on the guards. This standard does not apply to pole trailers, pulpwood trailers, low chassis vehicles, special purpose vehicles, "wheels back" vehicles, or temporary living quarters.
Objectives Evaluate the effectiveness of the new rear impact guard safety standard. Compare the crash performance of guards on trailers meeting the NHTSA standard and/or TTMA recommended practice to the smaller "pre-TTMA" guards on trailers meeting only the 1952 FMSCR standard. Compare the striking vehicle (car, pickup truck, SUV, or van) passenger compartment intrusion (PCI) underride rate of the "pre-TTMA" guard and the PCI underride rate of the new NHTSA and/or TTMA guard for trailers. Examine the crash performance of the rear-end structures of single-unit trucks. Estimate the cost per vehicle for the initial installation and subsequent maintenance of the rear impact guard. Examine the durability and reliability of the rear impact guard.
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. Because some type of rear impact guard was installed on most trailers even before the FMVSS 223 and 224 standards were in effect, a conventional "before vs. after" statistical study is unlikely to show significant differences. Statistical analyses of the effectiveness of the new NHTSA rear impact guard will be assessed using the State police accident reports and the NHTSA supplemental crash report forms, along with examination of selected cases from the NASS system. In addition, the long-term trends of fatalities in underride and rear-impact crashes will be studied in FARS. The cost for the initial installation of the rear impact guard will be estimated from "teardown" analyses or from information provided by manufacturers. Maintenance costs and durability of the rear impact guards will be studied in government and/or private trucking fleets.
Status. Collection of 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 and durability of the rear impact guards is underway.