ARLINGTON, Va. — The head restraints in about a third of all 1999 passenger vehicles are poorly designed. Only 1 in 20 of the 1999 cars, pickups, and utility vehicles earns a good rating for head restraint design. Disappointing as these findings are, they represent an improvement since 1997 models were evaluated. Then more than half of all passenger vehicles were equipped with head restraints rated poor. Both sets of evaluations were conducted by researchers at the Insurance Institute for Highway Safety.
"Some head restraints are getting better, but not nearly enough progress has been made," says Institute senior vice president Adrian Lund. "The manufacturers can easily turn their poor designs into more effective head restraints. They just have to make this a priority. The few automakers who have done so, mainly Volvo and Saab, are leaving the rest of their competitors behind."
Distribution of head restraint evaluations, 1997 and 1999 passenger vehicles
Cars with head restraints rated good include the BMW Z3 Coupe, Saab 9-3 and 9-5, Volkswagen New Beetle (some seat options), and Volvo C70/S70/V70 and S80 models. Among pickups, only the Chevrolet S10 and GMC Sonoma have good restraints. And among utility vehicles, only the Chevrolet Blazer (some seat options) and Mitsubishi Montero earn good ratings.
The necessary first step toward an effective head restraint — one that reduces the risk of whiplash injury in rear-end crashes — is a good geometric design. "A good design means the restraint is positioned behind and close to the back of an occupant's head so it's where it needs to be to provide protection in a rear-end crash," Lund explains.
What determines good head restraint geometry
Two criteria determine good head restraint geometry. One is height — the top of a restraint ideally should be as high as the top of an occupant's head. The second criterion is backset, or the distance between the back of an occupant's head and the front of the restraint.
The Institute rates head restraints good, acceptable, marginal, or poor based on these two criteria. The rating for a fixed head restraint is straightforward — the zone into which its height and backset place it also defines its rating in relation to an average-size male. The rating for a restraint that adjusts in height and/or backset depends on whether it locks in the adjusted position. If it doesn't, its rating is defined by height and backset in the down and/or rear position. If an adjustable restraint does lock, its height and backset are measured in both the down position and the most favorable locked position. The final rating is the better of these, except that if the adjusted rating is used it's downgraded a category because so few motorists adjust their restraints. The exceptions are some Mercedes models, which aren't downgraded because they adjust automatically, and Saabs because Institute research indicates these restraints are effective even in the down position.
Ratings based on geometry predict head restraint effectiveness in real crashes: Separate Institute research indicates that the head restraint evaluations based on geometry are good predictors of how well people will be protected in rear-end crashes. A study of more than 5,000 insurance claims for rear-end crashes found that drivers of vehicles with head restraints rated good are significantly less likely to claim neck injuries than drivers in vehicles with poor restraints.