It’s Keirin weekend!

Keirin is a mass-start track cycling event in which 6-9 sprinters compete at one time in a race with a paced start. Riders draw lots to determine starting positions and start as the pacer (which could be a motorcycle, a derny, or a tandem bicycle, for example) 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.

Source: wiki