Head restraints, or headrests, may well be the most underutilized safety device in your vehicle. Their purpose is to prevent soft tissue or "whiplash" injuries by stopping your head and neck from overextending in the event of a crash.
But, they only work if they're adjusted properly. Keep in mind that a properly adjusted headrest and a correctly positioned seat can reduce whiplash injury to a minimum.
The upper edge of the headrest should be the same height as the top of your head. The distance between your head and the headrest should be as small as possible, and should not exceed four cm. Don't forget to adjust your rear seat headrests as well, if your vehicle is equipped with them.
Unfortunately, not all vehicle models (particularly older model years) have headrests that can be properly adjusted. To find out more about head restraints and which vehicles are equipped with head restraints that provide the best protection, visit the Insurance Institute for Highway Safety's website.