A proposed quasi-static test for improving the crash performance of trailer rear underride guards

Abstract

Current U.S. and Canadian regulations for rear underride guards on large truck trailers do not promote designs with adequate protection in offset crashes. The objective of the current study was to determine whether a quasi-static evaluation could distinguish between underride guards with different performance in offset crash tests. Five different underride guard designs were evaluated in quasi-static testing. These designs were previously tested in 56 km/h impacts with a midsize passenger car with 30 or 50% overlap. Three of the guards exhibited marginally passing performance in the crash test, with car excursion under the rear of the trailer reaching the base of the windshield but stopping prior to trailer-to-dummy contact. The other two designs failed to prevent trailer-to-dummy contact. Two quasi-static test configurations were assessed for their potential to distinguish between the marginally passing and the failing designs: the outboard P1 test in the existing regulation and a new 20-degree-angled test developed using crash test acceleration measurements. In both configurations, the guard designs with marginally passing crash test results demonstrated higher force and energy levels than the designs with failing crash test results. However, the 20-degree-angled test showed greater differentiation between levels of crash test performance while also producing more representative damage patterns. Underride guards that prevented trailer-to-dummy contact in the crash tests sustained quasi-static force levels of a least 100 kN prior to 75 mm of displacement in the 20-degree test. Rear underride regulations could be improved by replacing the outboard P1 test with a 20-degree-angled load applied to the end of the underride guard. This evaluation also could supplement or replace underride guard crash tests conducted by the Insurance Institute for Highway Safety (IIHS).