More airbags may not be better.
An IIHS study released Wednesday concluded that knee airbags didn't significantly reduce the risk of injury in real-world crashes, and test data from the agency may show that the supplemental airbags may have increased injury rates in certain crashes performed by the insurance industry-funded agency.
“There are many different design strategies for protecting against the kind of leg and foot injuries that knee airbags are meant to address,” Becky Mueller, an IIHS senior research engineer, said in a statement. “Other options may be just as, if not more, effective.”
The IIHS compiled crash data from 14 states involving vehicles with and without knee airbags and concluded that knee airbags reduced the overall risk of injury from 7.9 percent to 7.4 percent, which the IIHS concluded wasn't statistically significant.
In more than 400 crashes performed by the IIHS on new vehicles, knee airbags increased the risk of lower leg injuries and right femur injuries in driver-side small- and moderate-overlap crash tests but reduced the risk of head injuries. The IIHS said that knee airbags may be included by carmakers to reduce injuries in unbelted passengers by distributing impact forces across both legs. The knee airbags are also designed to reduce the risk of upper body injuries by controlling lower body movement.
The IIHS said its compilation of real-world crash data did not examine whether passengers were belted in at the time of impact, however.
Many automakers, including General Motors and Toyota have installed driver-side knee airbags on most of their new models for several years.