Canadian Underwriter

This airbag might increase injury risk

August 12, 2019   by Adam Malik

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Airbags, including knee, deployed in a Volvo XC40 during crash testing by the IIHS.

A relatively new attempt to lower the risk of injury in a collision has been panned by a safety group.

The Insurance Institute for Highway Safety (IIHS) recently reviewed knee airbags – something that has grown in popularity of the last decade with about half of all vehicles in 2017 being equipped with at least one on the driver side. However, it has been untested in real-world scenarios.

The organization found that not only did knee airbags not reduce bodily injury by any significant margin, it actually could elevate the injury risk. Unlike curtain airbags or those in steering wheels, knee airbags aren’t thought of as lifesaving.

“Leg injuries in a car crash may be debilitating but don’t often kill people. So even as we’re looking at the real-world data and saying, ‘What kind of benefit do these knee airbags have?’ we’re not going to be seeing those dramatic differences,” Becky Mueller, IIHS senior research engineer in Virginia, told Canadian Underwriter.

“The big assumption is that people think more [airbags] is better. This study is indicating in this case more may not necessarily provide you with additional benefits.”

The IIHS took data from 414 front-end crash tests to figure out injury probability for 12 body regions. Researchers then looked at data from police-reported crash information compiled from more than a dozen states in the U.S. to compare injury risks between vehicles that were equipped with knee airbags and those that weren’t.

In testing, researchers found that the airbags actually played a role in increased risk for lower leg injuries and right femur injuries. Head injury risk, however, was reduced slightly, they noted.

In real-world analysis, injury risk was reduced by just half a percentage point to 7.4%, something the IIHS called a statistically insignificant result.

The knee airbag deploys from the lower part of the dashboard, below the steering wheel. It’s intended to distribute impact forces to reduce leg injuries. It is also believed that the airbags could help reduce the force on an occupant’s chest and abdomen by controlling movement of the lower body.

Mueller did note that more study is needed to figure out exactly what kind of injuries could be caused by knee airbags.

“There may be other technology like redesigning the shape and how soft the instrument panel is that may be just as effective at reducing leg injuries as putting an airbag in that position,” she added.

So why have knee airbags? Carmakers have installed them in order to pass safety testing with unbelted crash test dummies. As the IIHS always tests crashes with fully belted dummies, it couldn’t confirm whether or not someone without their seatbelt buckled would actually benefit from a knee airbag in the event of a crash.

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