U.S. motor vehicle regulations pertaining to occupant head restraints have gone unchanged for about two decades, but soon they will get a massive overhaul.

Seat suppliers currently are studying and scurrying to meet the new code, FMVSS 202A, and U.S. auto makers are in the throes of deciding the best way to satisfy the new mandate.

The code applies to front seats for all vehicles produced on or after Sept. 1, 2008. Rear seats for all new vehicles must be in compliance by Sept. 1, 2010.

The new code is designed to improve head restraints to minimize potential whiplash injuries, which occur frequently in low-speed, rear-end collisions below 10-15 mph (16-24 km/h).

In a rear-end collision, the occupant's head rotates rearward, then thrusts forward (as much as 30°), damaging the soft tissue in the neck. The new federal code restricts head-to-chest rotation to 12°.

Crashes at higher speeds generally produce injuries more severe than whiplash.

Each year, U.S. vehicle occupants endure some 1.5 million rear-end crashes, resulting in about 2,000 deaths and 950,000 injuries.

Whiplash costs insurance companies some $8 billion per year in the U.S. — even more in Europe — and the new code is meant to minimize injuries in rear-end accidents, particularly those at low speeds.

Suppliers and auto makers have two design options to comply with the new code. Head restraints can remain static, as most of them are in vehicles today, but they must be taller and positioned closer to the head.

Also, they must integrate some type of internal structure, such as a plastic core, for better support.

The other option is an active head restraint that pivots forward at impact to meet the occupant's head as it thrusts rearward.

Videotape of crash tests with this type of restraint shows the head stays upright and doesn't thrust forward or back, minimizing the threat of whiplash.

Lear Corp., a fixture in the automotive seat market, is advocating the active head-restraint route, suggesting larger static devices will obstruct vision, present significant styling challenges to interior designers and frustrate consumers, who will find it difficult to wear hats while in the vehicle.

“The static solution will lead to unhappy consumers,” says Gerald Locke, Lear's director-safety engineering. “It will disaccommodate a certain percentage of consumers.”

Lear's proposal for an active solution requires no change at all to the head restraint, itself. Instead, the seat frame is modified to detect when an occupant's torso thrusts rearward when a vehicle is struck from behind.

At that point, the head restraint pivots up and forward to meet the occupant's head.

Lear calls the purely mechanical device ProTec PLuS because it triggers when an occupant's pelvis, lumbar and shoulders press against the seat back during a crash.

Lear's first-generation ProTec active head restraint is a simpler mechanism that pivots forward based solely on input from shoulders pressing against the seat back.

Since ProTec production began in 1998, Lear has sold some 5 million active head restraints, Locke says. They are in vehicles today for the Opel, Saab, Jaguar, Nissan, Peugeot, Citroen and Land Rover brands. The Saab 9-5 sedan in 1998 was the first vehicle to carry Lear's ProTec active head restraint.

The new ProTec PLuS was ready for market in 2003. Lear has a customer that will begin using the device next year for an '08 model vehicle, Locke says.

Auto makers appear to be heading in different directions in deciding how to meet FMVSS 202A as well as two other head-restraint standards as spelled out by the Insurance Institute for Highway Safety (IIHS) and the European New Car Assessment Program (Euro NCAP).

Each standard has a different emphasis, creating a complex web of crash testing and biomechanical data.

The IIHS studies the geometry of a vehicle's head restraint to see if it is large enough and positioned properly to prevent injury.

The IIHS says a restraint should be at least as high as the head's center of gravity, or about 3.5 ins. (9 cm) below the top of the head. The backset, or distance behind the head, should be as small as possible, the IIHS says, adding that backsets of more than 4 ins. (10 cm) have been associated with neck injury in crashes.

The IIHS also issues dynamic ratings for head restraints based on their performance in crash tests. The geometric and dynamic ratings are used to determine an overall ranking of good, acceptable, marginal or poor for a vehicle's head restraint.

Locke says Euro NCAP is the most difficult head restraint code to meet, incorporating much of the IIHS requirements and requiring three crash tests.

“And no one knows which one is the most representative of real-world crashes,” Locke says of the three codes. “They don't align perfectly with each other.” In other words, a head restraint that performs well according to one requirement may fail another.

Locke says ProTec PLuS is one of the few head restraints designed specifically to simultaneously comply with both IIHS and FMVSS 202A.

After a collision, the device resets itself in seconds after the torso rebounds, requiring no costly visit to the dealership, Locke says.

Other active head restraints require pyrotechnics and must be reset by an authorized technician, much like a deployed airbag after a collision.

A pyrotechnic device also requires seat designers to provide access to the back of the seat for repair work.

Most European and Asian auto makers already have decided how they will meet the new head restraint code, but Detroit's three auto makers continue their evaluations of the technology options, Locke says.

He says one auto maker has said it will purchase an active head restraint for the '09 model year, but Lear has not yet received the purchase order.

In some other vehicle programs, auto makers are choosing static head restraints to meet 202A, Locke says.

Lear can integrate its active head restraint technology in another supplier's seat or seat frame, if an auto maker so chooses, Locke says.

In an attempt to reduce cost, Lear also has a lower-priced version of the active head restraint, known as ProTec PLuS 2, which appears now in the new '07 Hyundai Santa Fe cross/utility vehicle.

Other new vehicles with active head restraints include the Mercedes S-Class, Volvo S80, Honda Civic and Acura RDX and MDX CUVs.

Locke says the auto industry has two additional years before FMVSS 202A rules take effect (in 2010) with regard to back seats because so many second- and third-row seats in minivans and SUVs now fold flat, occasionally hampered by protruding head restraints.

“The government has given us two extra years to figure out how to fold and tumble second- and third-row seats,” he says.