Seatbelts work by limiting body movement during changes in the speed or direction of vehicles, and were first offered by Ford Motor Company in 1956. By 1964, seatbelts were standard in all vehicles sold in the United States. Most modern seatbelts contain a lap and shoulder belt to keep occupants firmly positioned in seats, while utilizing a three-point harness system. Shoulder belts are attached to the end of the seatbelt buckle, which run up the side of the vehicle to an anchor point behind the front seat. A receiver in the middle or side of the seat locks the belt into place.
Seatbelts use pretensioners, which remove slack from the seatbelt during a crash.
Pretensioners activate milliseconds after a crash by increasing the belt's tension around the passenger. When buckling infants and children under 80 pounds into vehicles, pay close attention to the instructions that accompany their child and infant car seats. Some pretensioner systems require special seatbelting with the use of a clip that is supplied with the car seats. Never take for granted the safe use of a seatbelt system in conjunction with a child or infant car seat.