A new study by the Insurance Institute for Highway Safety (IIHS) found that the knee airbags showing up in more and more cars barely improve safety and can even have a negative effect on it.
The supplemental restraints pop out from the lower dashboard below the steering wheel and glove compartment and are intended to both protect the legs from impacts and help to hold the entire body in place. The costs of the equipment can be more than $100 per bag to car manufacturers and they can add hundreds to the price of airbag system replacements following an accident.
The IIHS found that in its driver-side small overlap crash tests cars, belted dummies in cars equipped with the bags actually had a higher rate of leg injuries than in those without them, although head injuries were reduced. Meanwhile, there was no positive effect during moderate-overlap evaluations.
Looking at real-world crash data, the rate of injury in cars with the airbags was reduced from 7.9 percent to 7.4 percent, but the IIHS said the difference was statistically insignificant.
One factor that needs to be considered, the independent organization said, is that the airbags are often part of an effort by automakers to meet federal safety requirements for unbelted passengers, and it’s possible that they provide a benefit in that scenario. However, according to the IIHS, 90 percent of drivers and 89 percent of front-seat passengers were buckled up in 2018.