Underride: living on the edge

THE scene is still fresh in our minds— almost 200 people killed or injured by bomb blasts at the Boston Marathon. Fresh, too, are the questions. What happened? Who is responsible? And perhaps the most elusive of them all: How could this be prevented?

Every injury, every fatality is tragic because human life is precious. It's why countless professionals are at work now, ultimately in search of ways to reduce the likelihood that a terrorist event like this will be repeated.

People died needlessly on a street in Boston April 15. And they die unnecessarily each day on streets and highways across America. The reasons vary. People text while driving. They drink while driving. They make errors in judgment while driving. The most recent statistics, compiled for the year 2008 by the University of Michigan Transportation Research Institute (UMTRI), indicate that 217 died when their light-duty vehicle ran into the back of a trailer. Like the tragedy in Boston, these deaths should not occur. And like the tragedy in Boston, there are professionals at work who are seeking ways to reduce the likelihood that people will die needlessly on America's streets and highways. They include automobile engineers, trailer engineers, independent research organizations, and government regulators.

Earlier this year, the Insurance Institute for Highway Safety (IIHS) completed a multi-year research project on the effectiveness of trailer rear impact guards. (See Page 16 for details.) The research involved crashing a Chevy Malibu into the back of trailers at 35 mph. IIHS tested the guards at three separate points. In the first round of tests, researchers slammed a 2010 Malibu into the middle of the underride guards. After that came another set of tests in which only half of the car hit the guards. In the third and final round, completed earlier this year, the cars were crashed into the corner edge of the trailers.

The tests showed, in general terms, that today's guards are doing what they are designed to do — prevent the light-duty vehicle from running under the trailer and keeping the rear of the trailer out of the passenger compartment. According to the data recorded on the instrumented test dummies, it's possible for human beings to drive a modern automobile into a current-day trailer rear impact guard at 35-mph and walk away.

But with a caveat. For a guard to do its job, the car must crash into it. The final round of IIHS crashes shows what happens when the car hits the trailer but engages only the outboard portion of misses the heart of the guard (the horizontal member plus an impact-absorbing vertical support).

This impact area of the final round of testing is quite narrow. A few inches one way, and the car engages one of the vertical supports of the underride guard, and underride is prevented, at least in this crash test. A few inches the other direction and the passenger compartment misses the trailer entirely.

It's not clear how many lives could be saved by reducing the likelihood of underride along the edge of a trailer. According to the UMTRI study published in 2011, a total of 65 people were killed in 2008 in underride collisions so severe that the trailer penetrated the passenger compartment, even with an impact guard. Underride along the edge of the trailer probably would be a small subset of that total.

But based on the results of the IIHS tests, it is possible to produce a guard that can prevent underride in the case of a severe offset, at least up to 35 mph. Manac's design, which features wider spaced vertical supports, did not allow underride in the third round of testing. We congratulate Manac. We also commend the IIHS for inviting trailer manufacturers and Trailer/Body Builders to witness these tests and to share the results. Information such as this helps trailer manufacturers design and build safer trailers.

Of course, the best way to protect against underride is to prevent the collision in the first place. One way to do that is to make the trailer more visible. A recent Wabash-Truck-Lite lighting project — essentially creating a center high-mounted stop lamp like those on light-duty vehicles — may improve truck safety by helping drivers notice that the trailer in front of them is braking.

But that only helps when drivers are watching. We fear that the motorists will find it increasingly difficult to stay focused on the road as they tinker with cell phones, GPS systems, and dash-mounted entertainment centers. As these distractions become standard equipment on their vehicles, drivers are going to find it harder than ever to focus attention on the big rig in front of them.

Ultimately safety features such as adaptive cruise control and even driverless cars will be the best guard against distractions — and underride. But until humans move over to the passenger seat, people will continue to ask, “How could this have been prevented?”

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