A seat belt (also known as a seatbelt or safety belt) is a vehicle safety device designed to secure the occupant of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt functions to reduce the likelihood of death or serious injury in a traffic collision by reducing the force of secondary impacts with interior strike hazards, by keeping occupants positioned correctly for maximum effectiveness of the airbag (if equipped) and by preventing occupants being ejected from the vehicle in a crash or if the vehicle rolls over.

The world's first seat belt law was put in place in 1970, in the state of Victoria, Australia, making the wearing of a seat belt compulsory for drivers and front-seat passengers. This legislation was enacted after trialing Hemco seatbelts, designed by Desmond Hemphill (1926–2001), in the front seats of police vehicles, lowering the incidence of officer injury and death.

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