Seat belts have existed in different forms since the early days of automobiles,and they have changed from a single lap belt to the three-point seat belt we use today.In 1911 the first airplane seat belt was installed.Then,in the 1920抯 they were used in rarce-cars.By the 1930s,a group of American physicians created lap belts for their own vehicles and urged vehicle manufacturers to provide seat belts on all vehicles.

　　Dr.C.Hunter Shelden made a major contribution to our safety with his article in the November 5,1955 Journal of the American Medical Association (JAMA).He strongly encouraged the manufacture and use of door locks,airbags,and retractable(伸缩式的) seat belts,like the ones we use today.The modern three-point seat belt,including a lap belt and a shoulder belt,was introduced as standard equipment on Volvo cars in 1959.

　　In 1970,the state of Victoria in Australia made the wearing of a seat belt compulsory for every car driver and front-seat passenger.Today many countries have also mandated(授权) the use of five-point safety harnesses for carefully designed child safety seats that can protect a child during a serious car accident.

　　An airbag is a Supplemental Restraint System,or SRS,and consists of a rapidly inflatable restraint cushion that works together with a seat belt to protect you during a collision.Modern cars often contain several airbags in various locations.Since airbags can only inflate once and will quickly deflate after the initial impact,they will not provide any protection for you during a secondary collision.

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