The IIHS reported after controlling for driver age and gender and vehicle type and weight, a driver of a vehicle rated good for driver protection in a side impact is 70 percent less likely to die in a left-side crash compared with a driver of a vehicle rated poor. A driver of a vehicle rated acceptable is 64 percent less likely to die, and a driver of a vehicle rated marginal is 49 percent less likely to die.
"This was our first look at how our ratings correlate with actual crash data since we started side tests in 2003, and the numbers confirm that these are meaningful ratings," said Institute chief research officer David Zuby in a statement. "Vehicles with good side ratings provide occupants with far more protection than vehicles that do poorly in our test."
Studies of frontal crashes have shown similar results: Drivers of vehicles with good ratings in the Institute's frontal offset crash test are much less likely to die in frontal crashes.
Side-impact crashes accounted for 27 percent of passenger vehicle occupant deaths in the United States in 2009. Such crashes can be particularly deadly because the sides of vehicles have relatively little space to absorb energy and shield occupants.
In the IIHS test, a vehicle is hit on the driver side by a deformable barrier weighing 3,300 pounds and traveling at 31 mph. The barrier's height and shape are designed like the front of a typical SUV or pickup. Ratings are based on injury measures recorded on dummies, head protection, and vehicle intrusion during crash tests. In addition to looking at overall driver protection, researchers also looked at these components individually. They found that a vehicle's structure rating was by far the best predictor of fatality risk.
The IIHS lists all of its top safety picks at its website.