The flag that is waved to start a race is the solid green flag. The waving of a green flag is almost universally supplemented with the illumination of green lights (resembling traffic lights) at various intervals around the course, particularly on ovals. Before the use of starting lights in Formula One and most other FIA sanctioned or associated events, the national flag of the country in which a race is occurring, instead of a green flag, was used to signal its start. This practice is retained on occasion in the event of equipment failure, or simply as a tradition, such as at the 24 Hours of Le Mans.