When Virginia State Trooper Gary Dawson came upon the head-on crash in rural Culpeper County, the crumpled metal and shattered glass told him he soon would be ringing the doorbells of relatives to give them the tragic news. A smashed red sedan lay on one side of the two-lane road at the crest of a hill, a crushed burgundy convertible on the other. Ambulances and firetrucks pulled up to remove the bodies.

To Dawson's surprise, however, the two drivers had climbed out and were inspecting the damage. The reason Priscilla Vansteelant and Ronald E. Woody II survived also put the March 12 accident in the nation's record books: It apparently was the first in which both cars deployed air bags.

"These people were really lucky," Dawson said. He told the two drivers the air bags probably saved their lives especially Woody, who was not wearing a seat belt. Both drivers said they were bruised but had no serious injuries. Auto safety experts saw the outcome as a vindication of their 20-year battle with the auto industry over whether the government should require air bags, a fight that roiled through the Nixon, Carter and Reagan administrations.

"There is some benefit in being stubborn," said Chuck Hurley, vice president of the Insurance Institute for Highway Safety, an insurance industry-supported research group that lobbied for air bag requirements.

Federal law requires that virtually all cars sold in this coun try, beginning with 1990 models, have driver's side air bags or automatic seat belts for both front-seat occupants. The requirement is expected to be extended to light trucks and vans later this year. Industry experts expect air bags to become standard equipment because of buyer resistance to automatic seat belts.

Vansteelant, 39, who was driving east on Route 640, said yesterday that she remembers the silver air bag inflating with a "quick shoosh ... . It's a jolt but not a hard jolt, like when you were a kid and used to jump on the mattress." She crawled out the passenger's side because her door was crushed in. Police later charged her with driving left of the center line.

Vansteelant has agreed to appear in a public safety film about the accident with Woody, and said she thinks "they ought to make people watch films of accidents with air bags." Woody, 22, who was driving west on Route 640, does not remember the air bag inflating, but "there is no doubt in my mind that they work ... . I can't say enough about them." He said he also now uses seat belts.

Air bags inflate with nitrogen, a harmless gas, in one-twenty-seventh of a second, preventing the driver or passenger from slamming into the steering wheel or windshield. They deflate almost immediately. The bags are triggered by sensors in the bumper. Of the approximately 189 million vehicles on U.S. roads, almost 2.5 million cars are equipped with air bags, the insurance industry estimates. The new federal rule will increase that to about 3.3 million by the end of the 1990 model year the vast majority with air bags only on the driver's side.

Woody picked up his new car Friday afternoon a 1990 Chrysler LeBaron, with a driver's-side air bag. Both of the wrecked cars were 1989 LeBarons.

Chrysler Corp. Chairman Lee A. Iacocca, a longtime vigorous opponent of air bags who recently converted to the air-bag cause, used the Culpeper crash to tout the benefits of his cars at a news conference.

Consumer advocates recalled that Iacocca and Ford Motor Corp.'s chief, Henry Ford II, personally lobbied the Nixon administration to kill proposed air-bag rules, arguing that they would hurt American industry. They credited Iacocca's change of heart to the impending federal restraint requirement, whose roots date to the Carter administration. The Carter administration put in place a rule that would have required air bags or automatic seat belts in all new cars by September 1983, but the Reagan administration threw it out before it could take effect.

In 1983, the U.S. Supreme Court ruled that the Reagan administration had not justified its rejection of the Carter air-bag rule. The next year, then-Transportation Secretary Elizabeth Dole announced that the government would require some sort of automatic crash protection such as air bags or automatic seat belts unless states representing two-thirds of the U.S. population enacted mandatory seat belt-use laws.

Joan Claybrook, president of Public Citizen and head of the National Highway Traffic Safety Administration under Carter, said her group estimates that 40,000 lives were lost in the last five years because of the delay in the air-bag rule. "It's one of the great success stories," she said, "but it took 20 years."