What is Keirin?
Keirin (ケイリン?) is a track cycling event in which racing cyclists sprint for victory. Keirin originated in Japan in 1948; the first Olympic competitions in the sport occurred in 2000.
A keirin race is a mass-start race with 6-9 sprinters riders and a paced start. Riders draw lots to determine starting positions and start as the pacer (usually a motorcycle, a derny, or a tandem bicycle) approaches. The riders are required to remain behind the pacer, which starts at the deliberately slow speed of about 25 km/h, gradually increasing in speed and leaves the track approximately 600–700 meters before the end, at a speed of about 50 km/h. The first cyclist to finish the race is the winner (sometimes finishing at 70 km/h). Keirin races are about 2 kilometers in length (eight laps on a 250m track, six laps on a 333m track, and five laps on a 400m track).
In competitions, this event is often conducted in several rounds in order to reduce the number of competitors to one “final” round of 6–9 riders. Eliminated cyclists may get the opportunity to try again in the repechages.