Technologue: Headgames

I took one look at the new Dodge Journey's front seats and groaned. "Let me guess: That headrest meets the new 2009 standards, right?" I asked product team leader Larry Lyons. "Yes, but it's not the final design," he reassured me, implying there's still hope the production version will be less forward-thrusting and Volvo-hard. But brace yourself for some discomfort with your next head restraint (there's nothing restful about these new seats).

NHTSA reckons that 272,000 annual whiplash injuries are costing society $3 billion (insurance-industry figures bump that to $8 billion). Whiplash occurs in low-speed rear-end collisions when the seatback restrains the body but the head continues moving backward, rotating and straining the neck (at higher speeds the entire seatback generally fails and the head and torso move backward together). Comfy, cushy headrests located well behind your head prevent the horrible whiplash suffered in pre-1969 cars without headrests, but they still allow too much head rotation-especially when they're not properly adjusted.

The fix? A new testing standard mandating either a static test based primarily on geometric requirements or a dynamic sled test with performance criteria. The latter is optimized for those willing to pay for active head restraints that move forward in an accident, while the static one is for seats like the Journey prototype's, which don't react to accident forces. The cheaper ones now have to be much taller than before, topping out 31.5 inches above the hip point if they're not height-adjustable and a minimum 29.5 inches for adjustable ones (two to four inches higher than before). What's worse is the "minimum backset," or distance from the head to the restraint. Previously unspecified, new restraints must loom within 2.2 inches or less. They must also stop a 15-pound sphere moving at 15 mph within three milliseconds at 80 g or less. There goes your cushy headrest.

Active restraints can be moved farther away from the head and/or can be a bit cushier, as long as a harder core moves into position during an 8.8g impact in time to limit head rotation to 12 degrees relative to the body without inflicting a head-injury-criteria number over 500. To date, three different active or semi-active designs have been proposed. First to market were Volvo WHIPS and Saab SAHRs, which use the occupant's torso or pelvic motion backward into the seat to lever the head restraint up and forward to meet the head. It's an elegantly simple concept, but passing the new test poses challenges. BMW offers a pyrotechnically fired system that tilts the headrest forward along with the top of the seatback in the 7 Series. Mercedes-Benz offers an electronically triggered spring-loaded device on C-, M-, and R-Class vehicles that pops the headrest forward when needed. This system can be reset without tools. Both the BMW and Mercedes systems were developed by Grammer. Rear-seat head restraints aren't mandatory, but anything that looks like a headrest must meet the new head-restraint standards by 2010. Furthermore, if they can be lowered for visibility or stowage, they must fold forward so adults can't sit in the seat without putting the head restraint into position. Might this discourage fitment of rear head restraints, increasing rear-seat whiplash incidents?

Anyone who doesn't drive with the seatback reclined to a gangsta-lean position will likely find the new fixed head restraints annoying, so within a few years expect most seats to feature pricier active designs, further escalating the price of even the cheapest cars. NHTSA predicts the new legislation will prevent around 17,000 injuries per year-six percent of all whiplash cases. Is this good value for money/discomfort? I'm not so sure.