These are the official rules that dictate the displaying of flags on F1 tracks.
This is extracted from "Appendix H to the International Sporting Code - Recommendations for the supervision of the road and emergency services" as published from the FIA and available
4 - SIGNALING
In the supervision of the road, the Clerk of the Course (or his deputy) and the observation posts rely largely on the use of signals to contribute to the drivers' safety and enforce the regulations.
Signals are given in daylight by different coloured flags which may be supplemented, or under some circumstances replaced by, lights.
Black and white signal boards of similar dimensions to the flags may also be used for certain signals: these should be clearly specified in the supplementary regulations of the event concerned.
At night the flags may be replaced by lights and reflective panels, but all drivers must be made aware of this at a briefing beforehand. Yellow lights at each post are obligatory for events run at night (see paragraph 4.2. and Article 12).
The minimum size of all flags is 60cm x 80cm except the red and chequered flags which should be at least 80cm x 100cm.
4.1.1) Flag signals to be used by the Clerk of the Course or his deputy at the start line:
a) National flag:
This flag is normally used to start the race. The starting signal should be given by lowering the flag which, for standing start events, should not be raised above the head until all cars are stationary and in no case for more than 10 seconds.
Should the national flag not be used for any reason, the colour of the flag (which should not cause confusion with any other flag described in this Chapter), should be specified in the Supplementary Regulations.
b) Red flag:
This flag should be waved at the start line when it has been decided to stop a practice session or the race. Simultaneously, each observer's post around the circuit should also wave a red flag.
The red flag may also be used by the Clerk of the Course or his nominee to close the circuit (see Article 2.3.c).
This flag should be waved and signifies the end of a practice session or the race.
This flag should be used to inform the driver concerned that he must stop at his pit or at the place designated in the supplementary or championship regulations on the next approach to the pit entry. If a driver fails to comply for any reason, this flag should not be shown for more than four consecutive laps.
The decision to show this flag rests solely with the Stewards of the Meeting, the team concerned will immediately be informed of the decision.
This flag should be used to inform the driver concerned that his car has mechanical problems likely to endanger himself or others and means that the he must stop at his pit on the next lap. When the mechanical problems have been rectified to the satisfaction of the chief scrutinizer the car may rejoin the race.
This flag should be shown once only and is a warning to the driver concerned that he has been reported for unsportsmanlike behaviour.
These last three flags (in d, e and f) should be shown motionless and accompanied by a black board with a white number which should be shown to the driver of whose car the number is displayed.
Normally the decision to show the last two flags (in e and f) rests with the Clerk of the Course, however it may be taken by the Stewards of the Meeting provided that this is stipulated in the supplementary or championship regulations. The team concerned will immediately be informed of the decision.
These flags may also be displayed at places other than the start line should the Clerk of the Course deem this necessary.
4.1.2) Flag signals to be used at observation posts:
This should be shown waved only on instruction from the Clerk of the Course when it becomes necessary to stop a practice session or the race. All drivers are required to slow down immediately and proceed to the pit lane (or the place foreseen by the regulations of the Event), and must be prepared to stop if necessary. Overtaking is not permitted.
This is a signal of danger and should be shown to drivers in two ways with the following meanings:
Single waved: Reduce your speed, do not overtake and be prepared to change direction. There is a hazard beside or partly on the track.
Double waved: Reduce your speed, do not overtake and be prepared to change direction or stop. There is a hazard wholly or partly blocking the track.
Yellow flags should normally be shown only at the marshals' post immediately preceding the hazard.
In some cases however the Clerk of the Course may order them to be shown at more than one marshals' post preceding an incident.
Overtaking is not permitted between the first yellow flag and the green flag displayed after the incident.
Yellow flags should not be shown in the pit lane unless there is an incident of which the driver should be made aware.
This should be shown motionless to inform drivers that there is a deterioration of adhesion due to oil or water on the track in the area beyond the flag.
This flag should be displayed, for at least (depending on the circumstances) 4 laps unless the surface returns to normal beforehand. It is not however necessary for the sector beyond where this flag is being shown to show a green flag.
This should normally be waved, as an indication to a driver that he is about to be overtaken. It has different meanings during practice and the race.
- At all times:
- A stationary flag should be displayed to a driver leaving the pits if traffic is approaching on the track.
- During practice:
- Give way to a faster car which is about to overtake you.
- During the race:
- The flag should normally be shown to a car about to be lapped and, when shown, the driver concerned must allow the following car to pass at the earliest opportunity.
This flag should be waved and is used to indicate to the driver that there is a much slower vehicle on the sector of track controlled by that flag point.
This should be used to indicate that the track is clear and should be waved at the observation post immediately after the incident that necessitated the use of one or more yellow flags.
It may also be used, if deemed necessary by the Clerk of the Course, to signal the start of a warm-up lap or the start of a practice session.
In Chapter X of the "International Sporting Code" is clearly noted a so called flag marshal.