The flag most commonly waved to start a race is the green flag. In some motorsports, especially when starting lights aren’t used, a national flag may be waved instead to signal the start.

Quick answer

  • Green flag : the usual “go” signal in racing.
  • National flag : used in some series or as a backup when starting lights are unavailable.

Small note

Different racing series can use slightly different start procedures, but if someone asks generally, the answer is green flag.