Air Bags Work Better With Belts, Studies Say

Question: Why use a seat belt when driving a vehicle equipped with an air bag?W. D.

Answer: The short answer is that the shoulder belt will provide significant additional protection.

Studies of air bag effectiveness are problematic, partly because it is difficult to know why people don’t die in major crashes--whether it is an air bag or seat belt that accounts for survival. But use of both is clearly superior to use of either one by itself, studies show.

In 1991, 41,462 people died in motor vehicle crashes across the nation. Although it is impossible to put a price on human life, the annual cost of hospital and follow-up health care for surviving crash victims is put at $6.5 billion annually. Of course, the lost economic contribution of people who die makes the financial cost higher yet.

Under federal law, auto makers must incrementally improve so-called passive protection in new cars, largely because motorists have declined to wear their shoulder and seat belts. By 1998, driver-side air bags will be required in all new cars.

About half of 1993 model cars will be equipped with air bags. So far, research shows that air bags are significantly reducing traffic fatalities and serious injuries.

The Insurance Institute for Highway Safety, a trade group that has become a leader in safety advocacy, conducted a study that found that in frontal collisions from 1985 through 1991, driver deaths were reduced 29% in cars equipped with air bags.

Studies by the National Highway Traffic Safety Administration, a federal agency, show a somewhat smaller estimated benefit from air bags, but those studies still show air bags providing an additional margin of safety over shoulder belts used alone.

The insurance institute analysis concluded that 225 drivers’ lives were saved during the six-year period. The number is expected to grow significantly as more cars are equipped with air bags. If every car on the road had had an air bag in 1991, there would have been 3,000 fewer deaths. Another 1,000 lives would have been saved if vans, pickups and utility vehicles were equipped with air bags.

Air bags provided the most benefit for drivers of large cars, who experienced a 38% decrease in fatalities compared to drivers of cars without air bags; drivers of small cars had a 27% reduction.

The study showed that air bags provide significant protection for unbelted drivers, cutting deaths among this group by 31% compared to deaths of drivers of cars without air bags.

The bags, which inflate in one-twentieth of a second after a frontal collision begins, provide a cushion across the upper body, shielding the driver from the steering wheel. They relieve the significant forces across the torso and pelvis exerted by the shoulder harness during high-speed impacts.

The bags also improve safety when the driver is belted. The rate of driver deaths was 20% lower among belted drivers in cars with air bags than among belted drivers in cars without air bags.

A 20% reduction in deaths is significant, particularly when you consider that it involved only frontal collisions, the only type of collision in which an air bag is supposed to deploy. Frontal collisions account for about half of deaths involving occupants of passenger vehicles.

A shoulder harness offers significant protection in the other types of potentially lethal accidents--rollovers, side collisions and rear-end collisions. In many of those crashes, unbelted drivers are thrown out of the car or violently tossed about inside the car. In addition, frontal crashes often are followed by vehicle rollovers or rear-end crashes.