The National Highway Traffic Safety Administration (NHTSA) has promulgated a new underride regulation which became effective for heavy commercial trailers manufactured after January 26, 1998. Heavy trucks are excluded. Although this new rule is considered by many to be deficient in some respects (not as good as it could be), it certainly represents a safety improvement over the old Federal Motor Carrier Safety Regulation (FMCSR) 393.88, which has been in effect since January 1953 and will continue to be so for heavy trucks. The new rule is also compatible with the European and Japanese rear underride standards. A series of eight rear underride crash tests used as a basis for this new rule, demonstrated the effectiveness of an underride guard that minimally complied with the new rule at impact speeds of 30 mile per hour (mph). But in some of the tests the underride magnitude was such that passenger compartment intrusion (PCI) occurred. It has generally been considered that for effective underride performance PCI should not be allowed. This raises the question: how would this minimally compliant guard (MCG) perform at impact speeds greater than 30 mph which occurs quite frequently in the real world? This paper addresses this issue based on the previous eight NHTSA underride crash test results. The primary purpose is to illustrate the potential performance of the MCG at impact speeds above 30 mph, and also to demonstrate the effect of guard strength on underride magnitude. (A)
Abstract