Seat belts, or safety belts, are harnesses designed to secure vehicle occupants against harmful movements resulting from collisions or sudden stops on the road. They absorb the energy from sudden deceleration to spread the impact across the passenger's body, protecting against injury.

Lap belts are adjustable straps that go over the waist. Older model cars have lap belts, similar to those found on modern airplanes, while newer models generally are equipped with three-point belts.c

The three-point seat belt has a lap belt attached to a sash that goes over the shoulder, diagonally across the vehicle occupant's body. The first car fitted with a three-point seat belt system was the Volvo PV 544 in 1959.c

Some cars only use a sash or shoulder harness that goes across the shoulder. The first shoulder belt requirement from the Federal Motor Vehicle Safety Standards came in January 1968. Without a lap belt to accompany the sash, however, occupants are liable to slide forward in their seat and out from under the belt. This being the case, the majority of cars now use the aforementioned three-point belt system.c

The belt-in-seat system is where the harness is attached to the backrest of the seat. The first time a car with belt-in-seat belts was introduced was in the Mercedes-Benz SL in 1990.

Five-point harnesses are seen in child safety seats and racing cars where the lap belt is connected to two shoulder belts and a clip between the legs. NASCAR also used six-point harnesses for additional safety.c

George Cayley invented seat belts in the early 19th century, but Edward J. Claghorn was the first to patent the seat belt in 1885.

By World War II, seat belts were adopted in all military aircrafts.

Dr. C. Hunter Shelden came up with the idea of retractable seat belts in automobiles in the early 1950s in order to prevent head injuries.

In 1959, the United States Congress passed legislation that required all automobiles going forward to include seat belts in their design.

State laws have been put into place to ticket those who do not wear their seat belts. Laws vary state-to-state.c