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SUV Deaths Put Design of Seat Belts in Question

June 22, 2003|Ricardo Alonso-Zaldivar | Times Staff Writer

WASHINGTON — Federal officials say they suspect the current design of seat belts fails to provide adequate protection in rollover accidents and have launched a test program to improve the most familiar -- and critical -- piece of auto safety equipment.

The popularity of sport utility vehicles has propelled rollovers to the top of the safety agenda. Rollovers account for 2% of all crashes, but they are the leading killer of people in SUVs and pickups and are a major factor in the rise in highway deaths.

Industry and safety officials have long warned that drivers and passengers in top-heavy vehicles such as SUVs should take extra care to buckle up. That remains the best defense in a rollover. But there is growing recognition that seat belts are not fail-safe.

"You can slip out of the belt," said Joseph Kanianthra, research chief for the National Highway Traffic Safety Administration. "The belts are designed for holding you in place primarily in a frontal collision. In a rollover, suddenly gravity acts against you. The belt can give way and the occupant can go down."

The number of belted drivers and passengers killed in SUV rollovers rose from 327 in 1997 to 516 in 2001, according to the NHTSA.

One of the victims was Rosa Rodriguez of Cathedral City, Calif., who was killed last year after she lost control of her new SUV on Interstate 10 near Arizona.

Rodriguez was wearing her seat belt, as were husband Christopher and their three girls, records show. But that didn't save her or 10-year-old Mackenzie when the family's 5,000-pound Chevrolet Suburban rolled over. Rodriguez was killed in the vehicle and Mackenzie was ejected during the crash.

"There was no rain, no darkness, no other car," said Ramona Franco, Rodriguez's mother. "We don't understand it."

Engineers say they are trying to.

Some U.S. automakers are experimenting with a safety device -- called a pre-tensioner -- that would instantly take the slack out of seat belts in a rollover, keeping drivers and passengers more firmly attached to their seats. The new device goes a step beyond the standard locking of the seat belt that drivers feel now when they hit their brakes.

The action of the pre-tensioner would reduce the chances of people slamming their heads on the roof, door frame or some other part of the vehicle in the violent and often unpredictable wrecks.

"What we are looking at pre-tensioning for is to improve the protection people already have when they are buckled up," said Jim Boland, safety manager for Ford.

Seat belts are effective in preventing adults from being ejected in a rollover -- which is usually fatal -- but "you still see contact with the interior of the vehicle, even the roof, in belted occupants," Boland said.

Currently, belts are designed to lock down with the sharp drop in speed in a frontal collision. The forces generated in a rollover can be very different. A vehicle may accelerate before coming to a stop.

"The belt design of today is not designed to be holding you in place" in a rollover, said the NHTSA's Kanianthra.

That's where a pre-tensioner would come in.

Triggered by a crash sensor, pre-tensioners are used in some newer vehicles to increase safety in frontal collisions.

Most people have an inch or two of slack in their safety belts, and a pre-tensioner tightens the belts as the crash is taking place. In one design, a small explosive charge ignites gas in a chamber, which rapidly expands to drive a piston attached to a cable. The cable pulls the belts, taking out the slack.

In a head-on collision, pre-tensioners help keep front-seat occupants in the best position to benefit from their air bags.

Adapting pre-tensioners for rollovers would require some changes, Boland said. The main one would be the addition of a rollover sensor, more sophisticated than those now used to detect frontal collisions.

For SUVs, "it has to be able to discriminate between those cases where a vehicle is driving over uneven terrain and those where it's actually going to tip," Boland said. "That's where a lot of the research is at the moment."

Volvo has developed a pre-tensioner system for rollovers and introduced it last year as part of the safety package for its XC90 SUV for 2003.

Seat belts have evolved over decades. In the 1930s, some doctors began installing homemade lap belts in their own cars and advocating their general use. In the early '60s, many states began to require lap belts, and the federal government followed suit by the middle of the decade. In 1974, the NHTSA mandated three-point lap and shoulder belts in the front seats of all new vehicles. Other requirements followed for lap and shoulder belts in rear outer seats, and adjustable shoulder belts in front seats. The government estimates that seat belts have saved nearly 150,000 lives since 1975.

Manufacturers already recognize pre-tensioners as an improvement in seat belt technology. But there is no federal requirement for them.

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