2010 Chevrolet Malibu - IIHS rear impact with semi-trailer, NO underrideEnlarge Photo
2010 Chevrolet Malibu - IIHS rear impact with semi-trailer, severe underrideEnlarge Photo
According to the Insurance Institute for Highway Safety (IIHS), that's because the underride guards—those cheap-looking bars that hand below the load floor at the back of the trailers—often fail in crashes and allow the vehicle to keep going under the trailer.
And when those underride guards fail, death (even by decapitation) or serious injury is significantly more likely, since typically the upper part of the cabin crushes.
Just in 2009, 70 percent of the 3,163 who died in all crashes involving large trucks were the occupants of cars or other passenger vehicles, the IIHS says; and the National Highway Traffic Safety Administration (NHTSA) estimates that there are 5,000 injuries and about 423 deaths annually due to cars striking trucks from the back.
Furthermore, the Institute looked at 1,000 real-world crashes in 2001 through 2003 and found that of the 115 involving a car striking the back of a large truck or semi-trailer, 28 involved an occupant death, and 23 of those involved catastrophic underride—while only 25 didn't involve underride.
The IIHS proved—with its own recent tests—that while current Canadian standards are stronger than those in the U.S., with either standard the guards can fail in a collision. The issue? Under current certification standards, the trailer and guard system aren't ever evaluated together. There are also types of trucks that remain exempt altogether, the IIHS says, emphasizing that it's up to NHTSA to make some changes based on a petition the Institute is filing.
"Hitting the back of a large truck is a game changer," said Institute president Adrian Lund, in a release. "You might be riding in a vehicle that earns top marks in frontal crash tests, but if the truck's underride guard fails — or isn't there at all — your chances of walking away from even a relatively low-speed crash aren't good."