Crash tests reveal design flaws with 18 wheeler trailers

by Heygood Orr and Pearson

Recent crash tests conducted by the Insurance Institute for Highway Safety (IIHS) have uncovered a design flaw in the way that 18-wheeler trucks handle rear end collisions involving passenger vehicles. Problems with the way these trucks are designed may affect the crashworthiness of sedans and other smaller passenger vehicles that are involved in rear end collisions with the trucks, leading to fatalities or other injuries.

Most semi tractor trailers are equipped with an underride guard that prevents vehicles from going under the truck in the event of a rear end collision. In crash tests that were recently conducted by the IIHS on eight of the most popular 18 wheeler trailers on the market, all were effective at preventing underriding during a full width crash.

The IIHS also tested how these underride guards performed in accidents where the passenger car was only 50% and 30% aligned with the tractor trailer. Compared with the results of the full width crashes, these underride guards were significantly less effective when the automobile and 18 wheeler were not fully aligned.

Although all but one of the semi trailers was able to prevent the rear edge from impacting the passenger side of the car in the event of a 50% collision, the IIHS estimates that the driver of the vehicle would have been killed in all cases. During the 30% collision, only one of the rear guards was able to prevent the car from underriding the semi trailer.

Despite the problems cited by the IIHS in these crash tests, all eight of the trailers that were inspected by the organization would have passed US and Canadian crash standards. The tests highlighted the need for improved semi tractor trailers in order to correct the design flaws uncovered by the IIHS and help to prevent fatal 18 wheeler accidents.