The U.S. National Highway Safety Bureau first required automobile manufacturers to install lap belts for all seats and shoulder belts for front seats in 1968. However, most Americans did not regularly use safety belts until 1984, when the first state laws were passed mandating seat belt use. At present, there are 48 states in which it is illegal for a driver or passenger to travel without a seat belt (the exceptions are Maine and New Hampshire). Of those 48 states, 10 have primary enforcement, meaning that police can stop and ticket a motorist simply for not wearing a seat belt. The other 38 states with seat belt laws have secondary enforcement, meaning that police can only ticket people not wearing seat belts if they pull the car over for some other reason.
As of 1996, 75 percent of automobile occupants in states with primary enforcement regularly use seat belts; 63 percent of those in states with secondary enforcement regularly use seat belts; and 37 percent of those in states with no seat belt laws regularly use seat belts.
Sources: Safety and Health, vol. 144 (September 1991), p. 60; Savitskie, Jeffrey. Push is on to tighten state's seat belt law. The Detroit News, Jan. 2, 1996. [Online] Available http://detnews.com/menu/stories/30468.htm, July 17, 1997; U.S. General Accounting Office. Highway Safety: Safety Belt Use Laws Save Lives and Reduce Costs to Society, May 1992 (GAO/RCED-92-106), p. 9.