In an effort to prevent whiplash, U.S. regulators will require vehicle headrests to be higher and closer to the head by 2008.

The new rule won't require headrests in the back seat. Some safety advocates and Honda wanted back-seat headrests to be mandated, but other auto makers and seat suppliers were opposed.

The National Highway Traffic Safety Administration said the cost of requiring back seat head restraints was too high considering the few whiplash injuries in back seats. NHTSA Administrator Dr. Jeffrey Runge said drivers also have complained about visibility problems when they have back-seat head restraints.

"When we did our analysis, 90 pe rcent of the time there's nobody in the back seat of vehicles and the other 10 per cent of the time that there are, it's kids," Runge said. "But this doesn't stop manufacturers from putting it in their back seats. Based on their user profile, if it's a safe thing to do they'll do that."

NHTSA established rules for auto makers who install back seat headrests voluntarily.