ARLINGTON, Va. — An association of auto insurers wants U.S. regulators to require stronger underride guards on tractor-trailers, expand guards to more truck types, and not allow them to be certified separately from the trailers they’re attached to, among other suggestions.

In a letter to David Strickland, administrator of the National Highway Traffic Safety Administration, the Insurance Institute for Highway Safety said "current standards allow underride guard designs that fail catastrophically when struck by passenger vehicles at speeds that frequently produce minimal intrusion and injury risk" in other consumer frontal crash tests.

"Cars’ front-end structures are designed to manage a tremendous amount of crash energy in a way that minimizes injuries for their occupants," says Adrian Lund, Institute president. "Hitting the back of a large truck is a game changer. 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.

The NHTSA estimates that about 423 people in passenger vehicles die each year when their vehicles strike the backs of large trucks. More than 5,000 car occupants are injured.

Off-angle, even some of the strongest
guards allow underride, says IIHS

The institute recently conducted crash tests (SEE VIDEO HERE) evaluating three different semi-trailer rear guards – two of which, the institute notes, were also certified to more stringent Canadian Motor Vehicle Safety Standards.

The tests, which had a 2010 Chevrolet Malibu slamming into the back of trailers at 35 mph, show that the Wabash trailer performed the best out of the three.

While a Hyundai trailer’s guard bent forward, sheared its attachment bolts, and broke off when hit by the car dead centre, the Wabash stayed in place and absorbed the crash energy. "In the real world, this would be a survivable crash," says Lund.

However, things change when the car impacts from a different angle, according to the Institute.

Instead of head-on, the Institute also ran tests to see what happens when the car hits with only part of its front.

Again, Wabash performed well in a 35 mph test with a 50 percent overlap while Vanguard National and a Hyundai allowed "severe" underride.

However, at 30 percent overlap at the same speed, the Wabash trailer guard bent forward and allowed severe underride as well.

Had these been real-world crashes, there would be no survivors, Lund points out.

"This test shows that even the strongest guard left as much as half of the rear of the trailer vulnerable to severe underride," according to the full report. "The guard only worked as intended when the striking car engaged the center.

"Preventing underride in narrow overlap crashes like these might mean devising a new way of attaching guards to trailers to utilize the side rails, in addition to requiring manufacturers to conduct compliance tests with guards on trailers."

The Institute wants a "substantial increase" the quasi-static force requirements; require that attachment hardware remains intact throughout the tests; as well as investigate whether the maximum guard ground clearance can be reduced.

Furthermore, the Institute urged that guards be certified for the trailers they are designed. Specifically, Lund called for NHTSA to require that the trailer, underride guard, bolts, and welding be tested as a whole system.

"That’s a big part of the problem," he says. "Some manufacturers do test guards on the trailer. We think all guards should be evaluated this way."

As well, the government should evaluate whether the standards can be extended to more truck and trailer types, says the Institute.

More than half of the truck units in the crash causation studies were exempt from underride guard regulations, or would have been exempt if built after the rules’ effective date, according to the group.

While there are no requirements for sideguards on trailers, Canada began studying the possibility a few years ago but hasn’t yet acted on the findings.