Under-ride guards on tractor-trailers often fail in crashes, with deadly results, so the Insurance Institute for Highway Safety is petitioning the federal government for a tougher standard. "Hitting the back of a large truck is a game-changer," said the IIHS in a statement on Tuesday. "You might be riding in a vehicle that earns top marks in frontal crash tests, but if the truck’s under-ride guard fails — or isn’t there at all — your chances of walking away from even a relatively low-speed crash aren’t good."

An estimated 423 people in passenger vehicles die each year when their vehicles strike the backs of large trucks; nearly 5,000 are injured, according to the National Highway Traffic Safety Administration.

Even when your vehicle earns top marks in government or insurance crash tests, it’s important to know that your car remains vulnerable to unusual types of accidents.  For example, someone could rear-end you and push you into the back of a tractor trailer. 

The Insurance Institute for Highway Safety chillingly has illustrated this fact through a series of tests in which passenger vehicles rear-end the backs of some of America’s most popular tractor-trailers. 

The study concludes that it’s not the passenger cars, but the tractor-trailers that fail to keep passengers safe. Oftentimes, the guard rails on the back end of trucks failed basic requirements even though the rails were certified to U.S. and Canadian safety standards.