While there is no universal system of racing flags, most series have standardized them, with some flags carrying over between series. For example, the chequered flag is commonly used across motorsport to signify the end of a session, while penalty flags differ. FIA-sanctioned championship flags are the most commonly used internationally, covering championships such as Formula 1, the FIA World Endurance Championship and WTCC, and are adopted by many motorsport governing bodies.
The solid black flag is used to summon a driver to the pits. According to the corpus, this flag may be used for a variety of reasons, including a penalty for disobeying the rules, or because a car is suffering a mechanical failure, leaking fluid, smoking excessively, or exhibiting damage such as loose bodywork. The car number of the summoned driver is displayed at the finish line. While the flag can indicate immediate disqualification, it is also used to signal mechanical issues requiring a pit stop.
A driver may also be black-flagged for failing to maintain a reasonable minimum speed. In the 1969 Canadian Grand Prix, Al Pease was disqualified from a Formula One race for going too slow. Ignoring the black flag or the black-white cross flag may result in post-race disciplinary action in addition to disqualification from the race. This can include fines, probation, suspensions, and other penalties, depending on the severity of the situation.
Other black flags communicate specific warnings or mechanical issues:
Black flag with orange circle: Also known as the "meatball" flag, this indicates that a vehicle is being summoned to the pits due to serious mechanical problems or loose bodywork that presents a risk to other competitors. It is also used to indicate a violation of maximum sound levels.
Per-bend black-white flag: A diagonally divided black-and-white flag is displayed with a car number to indicate a warning. This can be for unsportsmanlike conduct, such as intentionally driving another car off the course, or for exceeding track limits. For example, Charles Leclerc was shown this flag for "bad sportsmanship" during the 2019 Italian Grand Prix. In the 2023 Austrian Grand Prix, drivers received the flag for exceeding track limits.
Black flag with white cross: Some leagues use this flag with a car number if a driver ignores other black flags for an extended period, indicating that the car is no longer being scored. In IndyCar, this means indefinite disqualification.
Historically, flags were the only means for race officials to communicate to drivers. Modern F1 cars and other high-end formula racing cars have information displays on their steering wheels that can flash "flag" to warn drivers of hazards. Many circuits also employ trackside flashing lights to signal flag status.