The Keirin is a variant of the sprint in which a higher number (usually 6–8, or 9 in Japan) of sprinters compete in a very different format. Riders are paced in the early laps by (and are required to stay behind) a Derny motorcycle, which slowly increases the speed of the race from 25 km/h to about 50 km/h. It then leaves the track with about 600–700 m remaining.