Accident Analysis and Prevention 39 (2007) 696–707 A recommended specification for heavy vehicle rear underrun guards Ali Osman Atahan ∗ Mustafa Kemal University, Department of Civil Engineering, Tayfur Sokmen Campus, 31040 Hatay, Turkey Received 20 August 2006; received in revised form 26 October 2006; accepted 26 October 2006 Abstract A large research program was carried out to evaluate the effectiveness of different heavy vehicle rear underrun guards. Based on the test results, a recommended underrun guard specification was developed to prevent passenger injuries in such accidents. Data obtained from a series of static and full-scale crash tests performed at the Transport Canada Research Center was used in the development of the specification. Four different underrun guard designs were used during the full-scale crash tests. Three different vehicle models representing sub-compact, compact vehicles and light trucks and vans traveling at 48, 56 and 65km/h relative speeds were used to impact underrun guards head on. The first 10 of the crash tests guard was attached to a simulated trailer while the last one performed using an actual truck. The results obtained from these tests show that a guard built to the minimum requirements of U.S. FMVSS 223 may not be strong enough to prevent passenger compartment intrusion especially in compact and sub-compact automobiles. This paper documents the tests performed, the results obtained and their analyses, and conclusions derived from these analyses. A recommended specification is prepared on the minimum performance that should be required for an effective underrun guard. © 2006 Published by Elsevier Ltd. Keywords: Underrun; Rear impact; Protection; Passenger compartment intrusion (PCI); Accident; Crash test; FMVSS 223; Specification; Standard 1. Introduction Rear underrun accidents take place when a relatively small vehicle, such as a passenger car, collides with the rear end of a much larger, heavier and stronger vehicle. During the collision, the frontal portion of the smaller vehicle slides partially or com- pletely under the rear of the larger vehicle. In the worst case, the smaller vehicle underruns the large vehicle long enough that the rear extremity of large vehicle enters the passenger compart- ment of the smaller vehicle. This phenomenon, referred to as “passenger compartment intrusion (PCI)”, frequently results in fatalities (see Fig. 1). Heavy vehicle rear underrun guards can be categorized as passive protective devices and are utilized on the rear end of heavy vehicles to minimize the amount of vehicle underrun, crash severity and amount of PCI during passenger car-large truck collisions. The U.S. National Highway Traffic Safety Administration (NHTSA) requires that most heavy-duty trail- ∗ Tel.: +90 535 252 7145; fax: +90 326 245 5499. E-mail address: aoatahan@mku.edu.tr. ers and semi-trailers manufactured for sale in the U.S. on or after 26 January 1998 be fitted with a rear impact guard meet- ing the requirements of Federal Motor Vehicle Safety Standard (FMVSS) 223 (NHTSA, 1999a). In most countries, including Canada and European Union, there is not an adequate speci- fication or standard that exists for heavy vehicle manufactur- ers to equip their trailers with a rear impact guard, with the exception of tanker trailers designed to transport dangerous goods which was developed primarily to protect the tank and its valves rather than the occupants in the colliding vehicle. This shows the level of consciousness in these countries toward this important transportation safety concern (Atahan, 2003a, 2003b). To review the issue of rear impact protection for heavy vehi- cles and to develop a specification for Canada and Europe, a large research project was initiated at Transport Canada Research Center (Boucher, 2000a). A major objective of this research project was to determine the minimum performance levels that a heavy vehicle rear underrun guard should have to prevent pas- senger injuries and whether the participating countries should adopt the same performance requirements that are mandated in FMVSS 223. 0001-4575/$ – see front matter © 2006 Published by Elsevier Ltd. doi:10.1016/j.aap.2006.10.016 RETRACTED