IIHS study finds that knee airbags are full of hot air

By comparing crash test data to real accident data, IIHS found that knee airbags don't do much to prevent injury.

Kyle Hyatt Former news and features editor
Kyle Hyatt (he/him/his) hails originally from the Pacific Northwest, but has long called Los Angeles home. He's had a lifelong obsession with cars and motorcycles (both old and new).
Kyle Hyatt
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Knee airbags may be increasingly common on cars, but they might not be that useful, according to the IIHS.


Airbags have been a fixture in cars for the better part of three decades now, and while they started out as a safety feature for drivers, they have since started to spread out throughout the vehicle to include the front passenger, side-impact airbags, curtain airbags and so on.

One increasingly prominent type of airbag is the knee protection airbag that deploys from the lower dash area to cushion an occupant's knees in the event of a serious collision. However, the benefit that knee airbags provide may be overstated, according to a report published Wednesday by the Insurance Institute for Highway Safety (IIHS).

To find out whether knee airbags actually prevented injury, the IIHS looked at data from more than 400 crash tests as well as numerous reports from real traffic collisions to see if manufacturers' claims that knee airbags would prevent leg injuries and help control passengers bodies better to reduce other injuries were true.

What the IIHS found was that there wasn't much difference between having those knee airbags and not having them. The real-world crash data showed that the airbags only reduced the probability of injury by 0.5% while the crash tests showed that in certain circumstances, they increased the likelihood of leg injury.

"There are many different design strategies for protecting against the kind of leg and foot injuries that knee airbags are meant to address," says Becky Mueller, an IIHS senior research engineer, in a statement. "Other options may be just as, if not more, effective."

So, if they don't do much, why are vehicle manufacturers going to the trouble and expense of installing knee airbags? Well, the IIHS reckons that they might have more efficacy on an unbelted vehicle occupant, though the agency didn't test for that because in IIHS crash tests, unlike in real life, the dummies are always wearing their seatbelts.

Check out the gory details in Honda's IIHS crash-tested HR-V

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Watch this: Ride in the back seat at your own risk