Race control talks to drivers through flags, waved by marshals and shown on light panels around the track and on the steering wheel display. Knowing them explains most of the sudden changes you see in a race.
- Yellow - danger ahead. Slow down, no overtaking. Double yellow means be prepared to stop.
- Green - the hazard is cleared; racing resumes.
- Blue - a faster car is about to lap you. Let it by.
- Red - the session is stopped. Everyone returns slowly to the pit lane.
- Red and yellow stripes - slippery surface: oil, water or debris.
- Black and white diagonal - a warning for unsporting driving.
- Black with an orange disc - your car has a problem. Pit now.
- Black - disqualified. Return to the pits.
- Chequered - the session is over.
Safety car
For a serious incident, a safety car leads the field at reduced speed while marshals clear the track. Overtaking is banned and the field bunches up behind it - which wipes out whatever lead the front-runner had built. That single fact makes safety cars the biggest source of race-changing luck in F1.
Virtual safety car
For smaller incidents a virtual safety car is used instead. There is no car on track: every driver must slow to a set pace, shown on their dashboard, and the gaps between them stay roughly the same.
Red flag
If the track cannot be made safe at speed, the race is stopped. Cars line up in the pit lane, and teams may change tyres and make limited repairs. The race then restarts - and if it cannot, points are awarded on the shortened-race scale.