The strongest guard prevented the passenger compartment from running beneath the truck if the car struck it in the center.

Trailers' Underride Guards Often Fail: IIHS

The Insurance Institute for Highway Safety has petitioned NHTSA to require stronger guards on tractor-trailers. Currently, the trailer, guard, bolts, and welding don't have to be tested as a whole system.

Crash testing done by the Insurance Institute for Highway Safety indicates the underride guards required at the lower rear end of tractor-trailers can fail in relatively low-speed crashes, the institute announced March 1. IIHS said it has petitioned the National Highway Traffic Safety Administration to require stronger guards.

"Cars' front-end structures are designed to manage a tremendous amount of crash energy in a way that minimizes injuries for their occupants," said IIHS President Adrian Lund. "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."

Photos of the tests are shown here. They were done by crashing a 2010 Chevrolet Malibu at 35 mph into three parked trucks' guards that meet U.S. and/or Canadian standards. (IIHS says the Malibu is one of its Top Safety Picks and earns a five-star safety rating in NHTSA's New Car Assessment Program.) The strongest guard, as designed, prevented the car's passenger compartment from running beneath the truck, and this would have been a survivable crash, Lund said. Still, this guard worked as intended only when the car struck the center of the guard.

The weakest guard -- manufactured by Hyundai Translead and certified to U.S. and Canadian standards -- allowed severe penetration. Its guard "bent forward, sheared its attachment bolts, and broke after the Malibu hit it in the center rear at 35 mph," according to IIHS.

The institute said NHTSA has estimated about 423 people in passenger vehicles die per year when their vehicles hit the rear of large trucks, and more than 5,000 passenger vehicle occupants are injured. "The aim was to see if some underride guards perform better than others and to identify what crash speeds and configurations produce different types of failure," Lund said. "Damage to the cars in some of these tests was so devastating that it's hard to watch the footage without wincing. If these had been real-world crashes, there would be no survivors."

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OH&S Digital Edition

  • OHS Magazine Digital Edition - September 2020

    September 2020


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