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Big Rig Safety Features Fail In Certain Rear Crashes

By Aaron Crowe

Big Rig Underride Crash Test

If you’re going to hit a big-rig tractor-trailer from behind, you’d better hit it straight in the center if you want to increase your chances of survival.

That’s one general conclusion from reading recent test results from the Insurance Institute for Highway Safety that show that passenger vehicles that crash into the back of large tractor-trailers are better protected when they hit the center of the underride guards on the back of trailers head-on than when they hit the far outer edge of the trailer. A $20 part may be all that’s needed to fix the problem.

An accident with a large truck, however, is never planned and a driver is lucky to have a second or more to react no matter what their speed.

The underride guards are meant to stop cars hitting the big rig from behind from sliding beneath the truck’s trailer in a crash. The horizontal guards do a good job when a car hits it straight in the center, the IIHS found.

But cars that hit the outer edge of the trailer — at 30% overlap and when half of the car overlapped the trailer — all but one of the trailers passed the test, according to the insurance institute, which is financed by the insurance industry.

“These things can do a good job if you’re fortunate to hit them on the spot” where they provide protection, says David Zuby, the institute’s chief research officer.

Otherwise, the underride guard often fails and instead of the guard absorbing the energy of the crash, the oncoming car’s windshield is the point of impact and the car can slide under the big rig. The airbags and seatbelts can’t do the jobs they were designed to do, and the windshield that has hit the big rig smashes into the front seat and can decapitate a driver. Watch the IIHS video of such a crash to see how damaging the safety feature failure can be.

“All the improvements in occupant protection that have helped drive down crash deaths in recent decades count for little when the front of a passenger vehicle ends up under a truck,” according to the IIHS press release. “When this happens, the top of the occupant compartment get crushed because the structures designed to absorb the energy of a crash are bypassed.”

A car’s engine compartment, also called the crumple zone, was meant to take such an impact. “That has to get crushed if you’re going to be protected,” Zuby says.

The tests involved a car hitting a parked truck at 35 mph. The guards would have also likely failed at higher speeds, Zuby says.

In its tests, the IIHS found that when the guards held up, the test car’s structure and airbags protected the crash test dummy in the driver’s seat. But when they failed, head and neck injuries were so high that real drivers would have died.

Of the 2,241 passenger vehicle occupants killed in large truck crashes in 2011, 260 died when the fronts of their cars struck the rears of trucks, the insurance institute reported. That’s down from 460 out of 3,693 in 2004, a decline it partly attributed to fewer people driving in a weak economy.

Federal crash data make it difficult to pinpoint how many of the deadly crashes involve underride, the IIHS says. But a 2011 IIHS study of 115 car crashes into the back of a heavy truck or semitrailer found that only about one-fifth involved no underride or negligible underride, and half had severe or catastrophic underride damage.

The underride guards can be improved simply by moving the vertical supports out more, which can take more of the impact in an overlap crash, Zuby says. Without enough support at the outer edges, the horizontal bar is just moved out of the way upon impact.

Trailer manufacturers have started installing stronger guards to meet tougher standards that trailers in Canada have had to meet since 2007 to withstand about twice as much force as U.S. trailers do.

The one trailer that passed in the 30% overlap in the IIHS tests was made by Manac, which sells trailers in the United States under the name Trailmobile. The 30% overlap test is the most challenging underride test, according to the IIHS, because “it is the minimum overlap under which a passenger vehicle occupant’s head is likely to strike a trailer if an underride guard fails.”

The supports of Manac’s underride guard are only 18 inches from the edge, is 20 pounds heavier and only costs $20, the insurance institute found.

For families of car crash victims looking to sue owners or manufacturers of tractor-trailers with faulty guardrail underrides, it can be a difficult case to win because the car driver can easily be seen at fault for driving too close and hitting the semi from behind, says Philadelphia attorney Scott Diamond, who specializes in personal injury law but has never had an underride case.

“It’s kind of hard to blame someone else for your fault,” Diamond says.

Dennis Schaefer, a personal injury attorney in Florida, says he settled a claim two years ago with a trucking company where a man whose family he represented was killed when his Corvette slammed into the back of a semi tractor-trailer. It appeared the driver hit the truck just left of center and overlapped on the left side, with the guardrail puncturing the windshield.

The car didn’t go under the truck, but spun into an adjacent lane and was run over by another semi, Schaefer says.

The claim wasn’t over a faulty guardrail or underride guard, but the plaintiffs claimed that the back of the truck didn’t have proper lights or reflectors.

The Corvette driver was intoxicated and speeding, Schaefer says — facts that a jury would likely give more weight to than how dangerous a truck is.

Aaron Crowe is a journalist who covers the auto industry for CheapCarInsurance.net.