Airbags are there to help make cars and driving safer by minimizing the amount of blunt-force trauma the human body absorbs in the event of a crash. They’re good and useful, but apparently not all airbags are as useful as they seem.

Knee airbags are there to reduce leg injuries. They can also control the movement of an occupant’s lower body, so forces on the chest and abdomen are lessened. This is the airbag the takes issue with.

The agency claims the knee airbag, which is becoming very common in many cars, “has a negligible effect on injury risk,” according to a . In fact, IIHS says the airbags might even increase it.

To find out more, researchers looked at crash test data, measuring over 400 frontal crash tests, and real-world crash reports, compiling them from 14 states and comparing injury risk in cars with knee airbags and cars without.

It found knee airbags to only have “a small effect on injury” measured by the IIHS dummies in the drivers-side small overlap front and moderate overlap front crash tests. The small overlap test yielded increased risk for lower leg and right femur injuries from knee airbags, but the head injury risk was reduced slightly. IIHS observed no effects on injury in the moderate overlap test.

Further:

In the analysis of real-world crashes, knee airbags reduced overall injury risk by half a percentage point, from 7.9 percent to 7.4 percent, but this result wasn’t statistically significant.

Automakers install knee airbags because it helps their cars pass federal safety tests while using un-belted dummies, which knee airbags probably benefit a lot, according to IIHS. The agency admitted, however, that it didn’t review crashes where people weren’t wearing seatbelts and the dummies were always belted in the IIHS tests.

I don’t know who in 2019 is still riding around without wearing a seatbelt, but if that’s you, buckle the damn belt. As for knee airbags, if anyone has a better solution, then I’m all ears.