One increasingly common type of airbag – the knee airbag – has a negligible effect on injury risk and, in fact, may even increase it in some cases, according to a recent study by the Insurance Institute for Highway Safety (“IIHS”).
Knee airbags usually deploy from the lower dashboard and are intended to distribute impact forces to reduce leg injuries. They also may help reduce forces on an occupant’s chest and abdomen by controlling lower body movement.
To find out if knee airbags improved safety, IIHS researchers examined both crash test data and information from real-world crash reports.
For the first part, they looked at injury measures from more than 400 frontal crash tests conducted as part of the IIHS vehicle ratings program to see if injuries were less likely when vehicles were equipped with knee airbags.
To look at real-world outcomes, they compiled crash reports from 14 states and compared injury risk in vehicles with knee airbags with risk in vehicles without knee airbags.
The IIHS said that it found that knee airbags had only a small effect on injury measures recorded by dummies in IIHS driver-side small overlap front and moderate overlap front crash tests. In the small overlap test, knee airbags were associated with increased injury risk for lower leg injuries and right femur injuries, although head injury risk was slightly reduced. The airbags had no effect on injury measures in the moderate overlap test, according to the IIHS.
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 was not statistically significant, the IIHS added.
“There are many different design strategies for protecting against the kind of leg and foot injuries that knee airbags are meant to address,” said Becky Mueller, an IIHS senior research engineer and co-author of the paper. “Other options may be just as, if not more, effective.”
One reason some manufacturers have been installing knee airbags is to help vehicles pass federally mandated tests with unbelted dummies. The IIHS acknowledged that it was possible that knee airbags would help unbelted occupants in real-world crashes. The IIHS said that its study did not look specifically at crashes in which people were not using seat belts, and that dummies always were belted in IIHS vehicle ratings tests.
Victoria Spears
Victoria Prussen Spears is senior vice president of Meyerowitz Communications Inc., a law firm marketing communications consulting company. A graduate of Sarah Lawrence College and Brooklyn Law School, Ms. Spears was an attorney at a leading New York City law firm before joining Meyerowitz Communications. She may be contacted at [email protected].