On September 1, 1998, the Intermodal Surface Transportation Efficiency Act of 1991 finally goes into effect. The law required that all cars and light trucks sold in the United States have air bags on both sides of the front seat.
Inspired by the inflatable protective covers on Navy torpedoes, an industrial engineering technician from Pennsylvania named John Hetrick patented a design for a "safety cushion assembly for automotive vehicles" in 1953. The next year, Hetrick sent sketches of his device to Ford, General Motors, and Chrysler, but the automakers never responded. Inflatable-safety-cushion technology languished until 1965, when Ralph Nader's book "Unsafe at Any Speed" speculated that seat belts and air bags together could prevent thousands of deaths in car accidents.
In 1966, Congress passed the National Traffic and Motor Vehicle Act, which required automakers to put seat belts, but not air bags, in every car they built. Unfortunately, the law did not require people to use their seat belts, and only about 25 percent did. Air bags seemed like the perfect solution to this problem: They could protect drivers and passengers in car crashes whether they chose to buckle up or not.
While Ford and GM began to install air bags in some vehicles during the 1970s, some experts began to wonder if they caused more problems than they solved. When air bags inflated, they could hit people of smaller stature--and children in particular--so hard that they could be seriously hurt or even killed. A 1973 study suggested that three-point (lap and shoulder) seat belts were more effective and less risky than air bags anyway. But as air-bag technology improved, automakers began to install them in more and more vehicles, and by the time the 1991 law was passed, they were a fairly common feature in many cars. Still, the law gave carmakers time to overhaul their factories if necessary: It did not require passenger cars to have air bags until after September 1, 1997. (Truck manufacturers got an extra year to comply with the law).
Researchers estimate that air bags reduce the risk of dying in a head-on collision by 30 percent, and they agree that the bags have saved more than 10,000 lives since the late 1980s. (Many of those people were not wearing seat belts, which experts believe have saved more than 211,000 lives since 1975.) Today, they are standard equipment in almost 100 million cars and trucks.