In the sport of auto racing, a "yellow flag" is used. It signals drivers to reduce speed, indicating that there is a hazard on the track, such as an accident or debris. During a yellow flag situation, drivers cannot overtake, and they must maintain a controlled speed until the track is safe again. This rule ensures the safety of drivers, teams, and officials. In some cases, a yellow flag might be followed by a green flag, which signals that racing can resume at full speed.