Study reveals flaw in 18-wheelers that puts car occupants in harm’s way

You can own the safest car on the roads — one that boasts the highest available safety rating — but if that car crashes into the back of an 18-wheeler, the chances of you being seriously injured or even killed are great. They’re so great, in fact, that the Insurance Institute for Highway Safety is asking the federal government to require manufacturers to fix a potentially deadly defect on some of their big rigs.

An estimated 423 people in passenger vehicles die each year when their cars collide with the backs of big rigs, according to the National Highway Traffic Safety Administration. Another 5,000 people are injured in these wrecks.

In a new study, the Insurance Institute for Highway Safety finds fault with steel guards on the backs of some big trucks; the guards are supposed to stop cars from sliding underneath the trucks. However, even at low speeds, the guards can fail — leading to the car’s occupants being hurt or killed, the study found.

A study by the Insurance Institute for Highway Safety showed that a safety component on some big rigs isn’t working properly, causing a car to “slide” underneath a truck in a test crash.

Last year, the institute conducted crashes where it slammed a 2010 Chevrolet Malibu — which carries the top five-star safety rating — into the rear of parked 18-wheelers equipped with three types of rear guards. All of the guards complied with federal standards.

In three of the crash tests, the heads of the dummies in the Malibu hit either the truck’s steel guard or the car’s hood after the guard was pushed into the car’s passenger compartment. In the tests, the “underride” guard of a Hyundai-made truck bent forward and broke after the Malibu collided with it at 35 miles per hour. On the other hand, a Wabash National truck built to Canadian specifications prevented the Malibu from sliding underneath the tractor-trailer’s underride guard.

The Insurance Institute for Highway Safety tested the Chevrolet Malibu because it represents a typical family sedan, and the car has earned the top crash safety rating from the National Highway Traffic Safety Administration. The impact speed in the test crashes was 35 miles per hour, the same speed used by the traffic agency in its test crashes.

“Cars are much safer today than they used to be because the front ends are engineered to absorb impact and protect the occupant, so in frontal crashes, people often are able to walk away,” says Russ Rader, a spokesman for the Insurance Institute for Highway Safety.

“But in a crash with the back of a big rig, where the underride guard gives way, people don’t have a chance. The impact point becomes the windshield, and you end up having the occupancy compartment peeling back as the vehicle goes under the truck.”

In 2009, more than two-thirds of the 3,163 people who died in all large-truck crashes in the United States were occupants of cars or other passenger vehicles.

Rader says the institute will ask the National Highway Traffic Safety Administration to make the guards safer. For instance, the federal government requires that underride guards be no more than 22 inches off the ground. Some of the safest underride guards are positioned even lower than that, Rader says, and some manufacturers of big rigs are voluntarily lowering their underride guards.

“We hope the government decides to act on our petition,” Rader says. “But even if they don’t, we think there is an opportunity for trailer manufacturers to improve the guards on their trailers. The main thing is we want the guard to catch the bumper of the striking car.”

Bill Graves, president and CEO of the American Trucking Associations, told CBS News that specifications developed decades ago to address the issue of cars sliding underneath big rigs “are probably not adequate today.”

In a statement, the National Highway Traffic Safety Administration says that in a 2009 study, it identified underride guards as one of the elements of crash safety standards needing improvement. The federal agency says the highway safety institute’s report “is consistent with our findings.”

As a result of its 2009 review, the National Highway Traffic Safety Administration says it initiated an analysis aimed at boosting vehicle safety standards. That analysis is scheduled to be completed in 2012.

–Kevin Lyons