Auto racing (also known as car racing, motor racing or automobile racing) is a sport involving the racing of automobiles for competition. The main aim of an individual event is to set the fastest time in a set number of laps or time limit. The finishing order is determined by race time, with the fastest time in first place, second-fastest in second place and so on. Any driver failing to complete a race for any reason is deemed "retired", or, more commonly, "out". Retired drivers will have their positions determined by the order in which they retired, with the first to retire finishing last, the next second-last and so on. In most events, a driver's final race position may be classified if he/she completes a certain amount of the race distance, usually just short of completing the full race (for example, in Formula One, a driver's race position is classified if he/she completes 90% of the full race distance). There are numerous different categories of auto racing, each with different rules and regulations, such as compulsory pit stops and car regulations, for all cars and drivers to comply. The continuous exposure of a driver to vibration and G forces in years of automobile racing may have a substantial effect on the high incidence of musculoskeletal disorders.