Red flag

A red flag stops the session immediately — all cars must slow to a controlled pace and return to the pit lane.

Shown when conditions make continuing unsafe: a blocked track, a serious accident, or weather bad enough that visibility or standing water becomes dangerous.

In a race the field forms up in the pit lane in running order, and cars may be worked on there — which is why a red flag can hand a free pit stop to drivers who had not yet stopped, and is one of the largest single strategic swings in the sport. Sessions restart either from a standing start or behind the safety car.