The blue or passing flag has different meanings depending on how it is held and whether it is used during practice, qualifying or racing. Generally when it is held motionless it is an indication to a driver that there is a faster car following closely behind, but not yet close enough for a pass. A waving flag generally indicates that the driver is about to be overtaken and should take care to permit the following vehicle a safe pass. Some drivers resist moving over for an over-taking car when they feel they are racing for position. Controversy can follow the use of the passing flag.
Some series use a blue flag with a diagonal yellow stripe.
This commonly means there is oil on the track. It also can mean water or another substance causing a change in the racing surface. The black and white flag is used in some series to indicate unsportsmanlike conduct. This is typically held motionless next to a pit board with the car number on it. The driver may be penalized when this flag is shown.