Motorists planning to disconnect their air bags if the government allows it may be left with something they didn't anticipate: less effective seat belts.
The seat belts on some newer cars were designed to work with their air bags, automakers say. Alone, they will not protect a person as well as an older-style belt in serious crashes.
The newer belts allow a person to travel forward a few more inches than older belts, since automakers installed air bags to cushion the person. If the air bag is removed, however, the person faces a greater risk of head or chest injuries from hitting the steering wheel or dashboard.
Although it is difficult to tell how many vehicles have the looser belts, General Motors Corp. - the largest U.S. automaker - says more than half the vehicles it produced in the past two or three years has them, as do a few Ford and Chrysler models. Some foreign automakers also use the looser belts.
Federal transportation officials are considering allowing motorists to disconnect air bags in response to five dozen air bag-related deaths. But automakers and safety advocates say disconnecting the air bags is generally a bad idea.
"It's like the human body. If you go out and take out a vital organ, you've disrupted the entire balance," said Mitchel Scherba, director of safety integration at General Motors.
"It's important for customers to know that if they choose to have an air bag deactivated, the overall effectiveness of their vehicle's restraint system will be diminished," he said.
Chrysler Corp. and Ford Motor Co. use such belts in less than 5 percent of their respective fleets, including the Dodge Avenger, Chrysler Sebring, Eagle Talon, Ford Probe and Ford Escort.
None of the auto or safety officials interviewed could quantify the effect of the redesigned belts on driver and passenger safety. "It will still provide valuable occupant protection," said Dave Giroux, a Ford spokesman
In minor or moderately severe crashes, the redesign of the belt won't make a difference, auto and safety officials say. However, in severe crashes a person is more likely to travel forward far enough to hit the dashboard or steering wheel, sustaining head and chest injuries, they said.
"In a high-speed crash, the belt would provide somewhat less protection," said Chuck Hurley of the National Safety Council.
A larger person would be more likely to be hurt in those circumstances than a smaller one, said Scherba, the GM safety official.
When used with an air bag as designed, the newer belt has some definite advantages over the traditional one, said Barry Felrice, director of regulatory affairs at the American Automobile Manufacturers Association.
Because it is looser, it is less likely to break a rib or collarbone in a severe crash, he said. "That is particularly of concern for elderly people."
In older cars without air bags, the work of restraining an occupant falls solely on the belt, said Phil Frame, spokesman for the National Highway Traffic Safety Administration, or NHTSA.
The newer belt can "give way a little bit so that the air bag takes up some of the force of the crash and spreads it out over a broader section of your body," Frame said. The result: fewer belt injuries.
NHTSA is deciding whether to allow motorists to have their air bags disconnected on demand. The proposal, unveiled by the agency in November, is the most controversial of its responses to the air bag dilemma.
Air bags have killed 38 children and 24 adults, mostly short women, in low-speed accidents that would not otherwise have been fatal. Most of the victims were unbelted, improperly buckled or in rear-facing child safety seats. However, the bags have saved an estimated 1,750 lives since 1986, federal officials say.
U.S. automakers oppose the proposal, and many safety advocates discourage a large-scale disconnection of air bags.
NHTSA now requires people to obtain its permission to get air bags deactivated. Applicants must provide a compelling reason to do so, such as having osteoporosis or too many children to fit in the back seat. More than 1,000 requests have been approved, Frame said.
Because so few air bags have been removed, the country's top crash investigator - the National Transportation Safety Board - has not examined how the redesigned belts work in accidents without air bags, said Elaine Weinstein, chief of the NTSB Safety Studies Division.
Frame, at NHTSA, offered this advice to adults: "The best thing to do is buckle your belt, leave the air bag alone, and stay a reasonable distance from your air bag - 8 to 10 to 12 inches away." Children ages 12 and under should always ride in the back seat, he said.
Felrice, of the auto industry association, said, "Almost all people are at greater risk if they deactivate an air bag. That's why we think deactivation should only occur with government approval."