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.