Rolling start

A rolling start is one of two modes of initiating or restarting an auto race; the other mode is the standing start. In a rolling start, the cars are ordered on the track and are led on a certain number of laps (parade or caution laps) at a pre-determined safe speed by the safety car. When race conditions are ready, the safety car will leave the track, and the race marshal will show the green flag, indicating that the field is allowed to accelerate. The safety car typically leaves the track some distance before the finish line, and a few seconds may elapse between the safety car's departure and the showing of the green flag. Cars must wait for the green flag to accelerate to race speeds. In the past, drivers would need to look for the flag, but in modern times this information is typically communicated to drivers via two-way radio, or at the proper acceleration zone, marked by a line or cone, determined at the pre-race drivers and mechanics briefing.

In international-level motorsport, races with rolling starts are typically started by the starter changing the starting lights from red to green after a specified number of green flag pace laps behind either a lead car or safety car. In this case the red lights are pre-illuminated part of the way around the final pace lap and are changed to green once the starter is happy with the composition of the field. International rolling starts may be aborted by leaving the red lights illuminated and the displaying of an "Extra Formation Lap" board and/or flashing yellow lights.

Rolling starts are often accompanied by several rules to prevent drivers from getting an unfair advantage during the start of the race. For example, drivers on the inside line cannot overtake cars on the outside until they have passed the start line. Drivers must stay behind the pace car and maintain their position within the field, unless entering the pits or given leave to go around. Furthermore, as the green flag nears and the pace car exits the track, drivers must maintain speed and position heading to the proper line. The lead driver cannot slow excessively to force trailing cars to bunch up, which would give the leader a jump on the restart.

Motorsports utilising a rolling start include , sports car racing, and several worldwide touring car championships. Formula sports tend to avoid the rolling start for the initial start of the race, mostly because of the physics and technology behind the sport (for example, being too close to the car in front for too long can cause overheating and engine problems), but also because of the quicker acceleration times, and bigger dangers behind accidents within the sport.

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