Vehicle seat/head restraint combinations earning top scores from the Insurance Institute for Highway Safety reduce injury claim rates by 11.2 percent, compared to vehicles with poorly rated restraint combinations, a new study found.

The study, released by IIHS and the Highway Loss Data Institute, concluded that top-rated restraint combinations markedly reduce the likelihood that someone will sustain neck injuries if rear-ended by another vehicle.

The study also underscored the dramatic improvement in such restraint quality in today’s vehicles. A decade ago, IIHS said, more than half of the seat/head restraints the institute evaluated were rated “poor” and just 9 percent drew a “good” score. In contrast, 95 percent of 2015 models earned a “good” rating and none were rated “poor.” IIHS credited its own ratings program, combined with stricter federal requirements for higher front-seat head restraints, for the overall improvement in such occupant protection.

IIHS rates such vehicle restraints as “good,” “acceptable,” “marginal,” or “poor” based on both front-seat head restraint geometry and test results. (To learn more about these test methods, click on the photo or link below the headline to watch an IIHS video from 2013.)

In the U.S., whiplash injuries are the most frequently reported type of injury resulting from crashes.

For the recent study, researchers used an insurance claim database of more than 600,000 rear-impact crashes to assess the likelihood of an associated injury claim. IIHS and HLDI based study results on 2001-2014 model-year cars and SUVs using property damage liability and personal injury protection claims.

“The injury-reduction benefits were greatest for good-rated seats/head restraints,” IIHS reported. “Those with acceptable or marginal ratings had injury rates that were 4.4 percent and 3.7 percent lower, respectively, than seats/head restraints rated poor.”

The safety benefit of higher-quality restraints was even more pronounced among women, who saw lower injury rates with “good,” “acceptable,” and “marginal”-rated seats compared with “poor”-rated seats. For men, only “good”-rated seats were tied to statistically lower injury rates.

Females are believed to be at a higher risk for neck injuries because of several physical differences, the study noted.

“Injury rates were 13 percent lower for women and 9 percent lower for men in vehicles with good-rated seats/head restraints,” IIHS said.