What are the rules about moving across the track in a sprint?

• Before the sprint: riders "may avail themselves of the full width of the track" but must leave space for the opponent to pass and avoid any move that could cause a collision or fall.
• During the final sprint: each rider "shall remain in his lane up to the finish, unless he has at least a clear cycle-length lead".
• No blocking: a rider may not make any manoeuvre to prevent the opponent from passing.
• The sprinters' lane: an opponent riding in it may not be challenged or passed on the left.
• Leaving the lane: if the leader leaves the sprinters' lane and the opponent tries to pass on the left, the leader may not come back down without a clear bike-length lead.
• Passing on the right: the passing rider may not crowd the rider in the lane or make them slow suddenly.
• Dropping in: a rider who starts the sprint outside the lane may not drop into it if the opponent is already there, unless a clear bike length ahead.
• The blue band: not part of the track. Using it to gain an advantage means relegation or disqualification.
• Who rules: the judge-referee, alone and immediately.
• The penalty: relegation, or disqualification for a serious or intentional fault.

The glossary has the sprinters' lane, the sprint, relegation and disqualification and the velodrome.

Two riders at over 70 kilometres an hour on a banked track have very little room for error. The lane rules give the leader the shortest way round in return for holding still in it, and tell the challenger exactly where they may go, so neither has to guess what the other will do.