New vehicle head restraints and seat back designs are reducing whiplash, the most commonly reported injury in auto accidents, according to an insurance industry study.

Head restraints in many older models have been too low and far from a motorist's head to protect against whiplash in rear-end crashes. But many models have redesigned head restraints and seat backs to keep the motorist's head and torso moving together when the vehicle is hit from behind.

The Insurance Institute for Highway Safety examined injury claims for those models before and after the improved head restraints and seat backs were installed and found whiplash claims were cut by as much as one-half.