Finally a long overdue vehicle safety improvement is happening. The designs of head restraints in more and more passenger vehicles are being improved so that many occupants are better protected from whiplash injury.
For years, head restraints were poorly designed. Most of them were adjustable, but even when they were adjusted to their highest positions they still weren't behind and close to the backs of many occupants' heads, which is where they need to be to protect the neck in a rear-end collision. Today more head restraints can be positioned correctly. The geometry is getting better. Still, many people don't adjust the positions of their restraints.
In 1995 the Institute began to rate head restraint geometry, finding only 3 percent of vehicles had good head restraints while those in 82 percent of new passenger vehicles were poor (see Status Report special issue: whiplash injuries, Sept. 16, 1995). These proportions have been changing steadily for the better. By the 2003 model year, 45 percent of passenger vehicles had head restraints rated good. At the same time, the percentage of vehicles with poor restraints had dropped to 10.
Head restraint improvements by model year
"This improvement shows automakers have gotten the message," says Institute chief operating officer Adrian Lund. "It used to be that unless you were short you'd have trouble finding a vehicle with head restraints that extended high enough to protect you. Now automakers are making improvements so that in many vehicles even taller people can position the head restraints where they need to be."
A well-designed restraint, in concert with the seatback, can reduce the risk of whiplash injury by reducing the differential motion of an occupant's head and torso in a rear-end crash. Unsupported, the head will lag behind as the torso is accelerated when a car is hit from behind. This differential motion can cause the neck to bend backward in a motion that resembles the lashing of a whip — the greater the torso acceleration, the more sudden the motion.
The necessary first step toward preventing differential movement between an occupant's head and torso is a restraint that's positioned as close to the back of the head as possible. Head restraints designed with poor geometry cannot be positioned this way for many occupants, so the restraints cannot begin to prevent whiplash injuries.
NHTSA lags behind
Since 1995 the Institute has been rating head restraint designs good, acceptable, marginal, or poor based largely on the geometric criteria of height and backset. In 2001 the Research Council for Automobile Repairs, an international consortium of research centers, agreed to a slightly modified version of the Institute's rating scheme, which now is in use internationally. But the U.S. government isn't keeping up. The National Highway Traffic Safety Administration's (NHTSA) head restraint standard is the same today as when head restraints first were mandated in 1969.
"The federal standard was weak to begin with when it first took effect almost 35 years ago, and now it's woefully inadequate. It lags way behind requirements in Europe," Lund says. "As long ago as 1974 NHTSA did propose upgrading the standard but then let the matter drop. The agency later began the rulemaking process over again and proposed a substantial upgrade in 2001, but once again the task hasn't been completed. More than two years have elapsed since the last proposal for upgrading this standard, and there's no final rule. It keeps being put off and then put off again. Where is it?" Lund asks. NHTSA's latest prediction for when it will issue a final head restraint rule is March 2004.
Improvements being made, room for more
With or without federal action, head restraints already are being improved — and geometry isn't the only aspect that's getting better. Some automakers are designing advanced head restraints that position themselves closer to occupants' heads or adjust seat stiffness to control torso movement in rear-end crashes. Some of these designs have been found to reduce neck injuries in real-world crashes (see "Not your father's head restraint: New designs reduce neck injuries," Oct. 26, 2002).
Such advancements are welcome, but Lund cautions that it's important to keep them in perspective. "Head restraints used to be almost uniformly abysmal, and now more of them are being designed to provide better occupant protection. It's commendable that almost half of all 2003 passenger vehicle models have good head restraints. But this still leaves more than half with head restraints rated less than good. And most of them have to be adjusted upward to provide even an adequate degree of protection. Every head restraint should be designed to protect the necks of people of a range of sizes in rear-end crashes."