For the most part, semi trailers have done a decent job of keeping vehicles from sliding underneath them, but when there’s an accident with only a small portion of the truck’s rear, a new study from the Insurance Institute of Highway Safety shows most trailers fail to prevent potentially deadly underride.
Underride guards are steel bars that hang from the backs of trailers to prevent the front of a passenger vehicle from moving under the truck in the event of an accident. Research has shown that the minimum strength and dimensions of underride guards are inadequate, which has prompted the Insurance Institute of Highway Safety (IIHS) to petition the National Highway Traffic Safety Administration (NHTSA) for tougher standards.
Recent IIHS crash tests have drawn attention to the inadequacies of the underride guards, and at least one manufacturer has started to improve on its guards. To see how the latest guards work, IIHS engineers put trailers from the eight largest manufacturers through a series of progressively harder crash tests.
In each test, a 2010 Chevrolet Malibu struck a parked truck at 35 mph. When aimed at the center of the trailer, all guards prevented underride; when aimed with only half of the car overlapping the trailer, all but one trailer passed. However, when the overlap was reduced to 30 percent, only the trailer manufactured by Manac passed. “Our tests suggest that meeting the stronger Canadian standard is a good first step, but Manac shows it’s possible to go much further,” said David Zuby, IIHS chief research officer, in a recent press release.
In a previous test conducted in 2010 and 2011, the weakest guard tested was from Hyundai where a guard broke when the Malibu hit it at 35 mph in a full-width crash. In a 50 percent overlap test, the underride guard on a Vanguard trailer allowed moderate underride at 25 mph, and severe underride at 35 mph.
“If trailer manufacturers can make guards that do a better job of protecting passenger vehicle occupants while also promising lower repair costs for their customers, that’s a win-win. While we’re counting on NHTSA to come up with a more effective regulation, we hope that in the meantime trailer buyers take not of our findings and insist on stronger guards,” commented Zuby.