In most forms of racing the checkered flag also ends the race for cars that have not yet completed the scheduled number of laps. Green Indicates the start of the race. The flagman will continue to show the green flag as long as the track is safe for competition. Often there are green lights around the track as well, to help keep the drivers informed. Red flag Indicates a dangerous situation on or near the track and the race is being stopped immediately.
Drivers are to bring their car to a stop quickly.
Rules governing working on the cars during a red-flag period vary. Yellow Tells drivers there is a problem on the track and they should slow down. At most tracks, scoring is frozen at the last lap completed under green-flag conditions, and racing under a yellow flag is not allowed. On most short tracks drivers continue around the track slowly until the officials re-establish the lineup and again show the green flag. On larger tracks a pace car usually comes onto the track after the cars slow and takes position in front of the current race leader.