IIHS tests side underride guards on semis (and the results are worth watching)

May 16, 2017

One year ago, in May 2016, Joshua Brown's Tesla Model S collided with the side of a big rig in Florida. The sedan's top was sheared off by the semi, killing Brown instantly. The car rolled 100 feet further before coming to a stop.

The story made headlines for months because Brown may not have been watching the road at the time of the crash, as he had turned on Autopilot, Tesla's semi-autonomous driving system. Pundits the world over pointed to the incident as an example of how far self-driving technology has to evolve before it's truly safe. 

But there was another factor in the crash, one that almost no one discussed: the truck's lack of side underride guards. If the trailer were equipped with those protective devices, the outcome of the collision could've been different.

In the U.S., rear underride guards have been required on trailers for decades. They were mandated following the grisly death of actress Jayne Mansfield, whose car slid beneath the back end of a big rig late one night in 1967. Though so-called "Mansfield bars" don't always work as well as they should, new tests from the Insurance Institute for Highway Safety show that their close kin, the side underride guard, could be a real life saver. 

Data shows that roughly half of all collisions between semis and passenger vehicles involve underride (i.e. a car passing beneath the semi's trailer in some way). Tests from 2012 showed that side underride guards could reduce fatalities in those instances by a whopping 90 percent. In real terms, that would save between 150 and 200 lives in the U.S. every year. 

To demonstrate the effectiveness of side underride guards, the IIHS recently ran crash tests involving two different semis. One was equipped with a conventional side skirt, which was only meant to improve a trailer's aerodynamics. The other was equipped with a similar-looking AngelWing device that concealed side underride guards. 

As you can see from the video above, the differences in outcome were dramatic. The IIHS explains:

"In both tests, a midsize car struck the center of a 53-foot-long dry van trailer. In the AngelWing test, the underride guard bent but didn't allow the car to go underneath the trailer, so the car's airbags and safety belt could properly restrain the test dummy in the driver seat. In the second test with no underride guard for protection, the car ran into the trailer and kept going. The impact sheared off part of the roof, and the sedan became wedged beneath the trailer. In a real-world crash like this, any occupants in the car would likely sustain fatal injuries."

With stats like that, should we expect side underride guards to become mandatory features on large trucks?

Given the current administration's reluctance to put new regulations on the books, it seems unlikely--at least in the near future. If the data continues to show that side underride guards can save lives, however, it's entirely possible that they could become standard offerings down the road. 

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