The guards on tractor-trailers designed to stop the back of a truck full of 20-gallon mayonnaise drums from decapitating you in a rear-end collision are often worthless even in crashes as slow as 35 mph, according to insurance industry tests.
The Insurance Institute for Highway Safety's (IIHS) research is the first in recent memory to look at so-called underride crashes. Federal data shows that about 420 people a year die and some 5,000 are injured from vehicles striking the back of semi trailers, and the IIHS estimates that roughly four-fifths of such crashes involve vehicles sliding under the back of trailers, raising the chances that the trailer will shear into the passenger space.
"You might be riding in a vehicle that earns top marks in frontal crash tests," said IIHS President Adrian Lund, "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."
The National Highway Traffic Safety Administration last updated the rules for underride guards 15 years ago, setting a standard that was not much tougher than what trailer manufacturers already met voluntarily and didn't apply to trailers made before 1998. Last year, the agency studied its own data and found there was no evidence its rules had saved lives. Yet other countries, including Canada, have written tougher requirements over the past several years
To test its research, the institute crashed a 2010 Chevy Malibu at 35 mph into three trailers, one built to U.S. rules, the other two certified to tougher Canadian standards for rear guards. The guard on the U.S.-certified trailer built by Hyundai Translead broke off in the collision, suggesting passengers in a real-world crash would have been decapitated.
Yet in the crash with a Wabash trailer that meets Canadian rules, the guard stayed in place and nothing intruded into the passenger compartment. The IIHS also ran off-set tests, in which all three trailers failed to some degree at keeping the passenger space of the Malibu intact.
The insurers want NHTSA to write a tougher rule for trailers, and apply it to older ones as well as new models. It also wants actual crash tests; the current standard applies only to the guard and its components in pieces, and doesn't test how well it prevents underrides after being installed. As for expense, NHTSA already has an idea on the lifetime costs of maintaining the current guards: just $15 each.