In motorsport, a safety car, or a pace car, is an automobile which limits the speed of competing cars or motorcycles on a racetrack in the case of a caution period such as an obstruction on the track or bad weather. The aim of the safety car is to enable the clearance of any obstruction under safer conditions, especially for marshals and/or await more favourable track conditions weather-wise. During a caution period the safety car (which generally consists of an aptly modified high-performance production car) enters the track ahead of the leader. Depending on the regulations in effect, competitors are not normally allowed to pass the safety car or other competitors during a caution period, and the safety car leads the field at a pre-determined safe speed, which may vary by series and circuit. At the end of the caution period, the safety car leaves the track and the competitors resume normal racing. The first reliance on this safety measure occurred with the deployment of a pace car during the inaugural Indianapolis 500 in 1911. Effect The use of a safety car has the effect of bunching competitors together, such as to eliminate any time and distance advantage that a leading driver may have had over the remaining field of competitors. This effect can make racing more competitive upon full race resumption; conversely, it has also contributed to faster leading drivers being negated just rewards for their efforts prior to the caution period. Subject to the racing regulations in force, it is not uncommon for drivers to be allowed to make pitstops during safety car periods. This situation may provide a strategic advantage since any scheduled refueling, tire change or maintenance may be carried out while other competitors are lapping at lower speed, and the drivers who pit then simply rejoin a queue of cars all running together. During normal racing conditions, such interventions would typically involve losing significant terrain over those drivers that remain on-track. Another notable effect of safety car periods is that racing cars consume less fuel until full race resumption, which can allow competitors to run longer distances on a tank of fuel than would otherwise have been possible and/or reduce the number of pitstops required for the duration of the race. Formula One Procedure In Formula One if an accident or inclement weather (typically, heavy rain) prevents normal racing from continuing safely, the Race Director