Seat belts have been proven to be effective in saving lives and preventing or lessening injuries in automobile accidents. The key to their success, however, is that occupants must use these safety devices. Because seat belts require active use by the wearer, inventors developed passive restraints to ensure driver and passenger safety. The first passive restraints were modifications of seat belts themselves; the belts were coordinated with operations of opening the car doors and starting the automobile, which caused belts built into tracks in the doors to wrap around the driver or passenger when the seat was occupied. Concurrently, the airbag was devised as a secondary form of passive restraint during impact.

In 1961, Arnold Kent of England considered the use of inflatable cushions. He suggested they could be stowed in front of the occupants and would inflate automatically from a container of compressed gas in the...