Knee airbags in modern cars are a common thing because many think they lower the risk of injury. But the all-important question is — do they really help?
Surprisingly, the answer is no. Even more surprisingly, in some cases, they may even have a negative effect.
In a new study conducted by the Insurance Institute for Highway Safety (IIHS), the researchers found that knee bags hardly improve safety, and in certain cases can increase the risk of injury.
For this study, IIHS examined data from its own crash test, as well as data obtained via real-world crash reports.
First, IIHS considered the injury measurements of belted dummies in more than 400 frontal crash tests. The researchers included two types of crash tests:
- Driver-side small overlap crash tests. In this test, the front left corner of a car going at 40 mph collides with an object.
- Moderate overlap front crash test. It replicates what happens when 40% of the total width of a vehicle going at 40 mph strikes a barrier moving at the same speed on the driver side.
In the first type of crash tests, IIHS noticed that the rate of leg injuries was actually higher in cars fitted with knee airbags than those without them, while the rate of head injuries was lower. Meanwhile, the use of knee bags didn’t have any positive effect in the cases of moderate overlap frontal crash tests.
Next, IIHS looked at real-world crash data. They found that the knee airbags lowered the risk of injury by 0.5%. However, this improvement, the researchers concluded, is too small to be statistically significant.
IIHS said that automakers often install knee airbags to pass mandatory safety tests involving unbelted dummies. It is very much possible that they are beneficial in such a scenario, but this is something we can’t say for sure because the IIHS didn’t check what happens when the occupants are not buckled up.