A driver at 300 km/h cannot read a message. He can read a colour. That is why a sport full of satellites and sensors still talks to its drivers with pieces of cloth.
Marshals stand around the circuit and wave them, and electronic light panels show the same colours at the same moment, so a driver sees the signal wherever he is looking. The colour tells him what to do before he can possibly see why.
Ignoring one is one of the few things in F1 that gets punished immediately and without argument, because a marshal is often standing on the track a few metres from a car that has stopped there.
| Flag | What it means |
|---|---|
| 🟡 Yellow | Danger ahead. Slow down and do not overtake. Two yellows waved together means the danger is serious and you must be ready to stop. |
| 🟢 Green | The danger has been cleared. Normal racing again from here. |
| 🔴 Red | Session stopped. Everybody slows right down and returns to the pit lane. Used for a crash that blocks the track or weather nobody can drive in. |
| 🔵 Blue | A faster car is about to lap you. Let it past. You are not racing that car — it is a lap ahead of you. |
| 🏁 Chequered | The session is over. In the race, the first car to cross under it has won. |
| Flag | What it means |
|---|---|
| Yellow and red stripes | The surface ahead is slippery — oil, water or debris. |
| ⬜ White | A much slower vehicle is on the track ahead of you. |
| Black and white, split diagonally | A warning for unsporting driving. Do it again and a real penalty follows. |
| Black with an orange circle | Your car is damaged or dangerous. Come to the pits and get it fixed. |
| ⬛ Black | You are disqualified. Return to the pits. It is very rare and it is the end of your afternoon. |
When a crash needs clearing but the race does not need stopping, a road car with orange lights comes out and leads the field round at a slow, fixed pace. Nobody may overtake it, so the entire field bunches up nose to tail and every gap a leader has spent forty laps building disappears.
There is a milder version called the virtual safety car, where no car comes out at all: every driver simply has to stay above a set lap time, so the gaps between them stay the same. Both are the reason a race that looked finished can turn into a fight with eight laps left.
Once you know the colours you stop needing a commentator to tell you what is going on. A yellow in one sector and a car missing from the timing screen means somebody has gone off there. A run of blue flags for the same driver, lap after lap, means his race is finished even if his car is not. A red flag means the teams are about to be handed a free tyre change and the whole strategy everyone spent Friday planning has just been thrown away.