Yellow flags
A waved yellow flag means there is a hazard on or near the track ahead. Drivers must slow down and must not overtake until they pass a green flag, which marks the end of the danger zone. Two yellow flags waved together mean the hazard is more serious and drivers need to slow down a lot more.
Yellow flags are shown at the marshal post just before the incident, and the same signal appears on the electronic light panels by the track and on the dashboard inside the car. If the hazard spreads into the next part of the track, race control can show yellows over more than one post.
Single and double yellows
The FIA's wording for the two levels is precise, and the stewards hold drivers to it.
A single waved yellow means: reduce your speed, do not overtake, and be prepared to change direction. There is a hazard beside or partly on the track. A typical example is a car that has spun and stopped on the grass, or a marshal standing by the barrier.
A double waved yellow means: reduce your speed significantly, do not overtake, and be prepared to change direction or stop. The track is wholly or partly blocked, or marshals are working on or beside it. You'll see double yellows when a crashed car is stuck in the middle of a corner or marshals are on the circuit clearing debris.
How much is "slowing down"?
This is where most penalties come from. The rules don't give a target speed. Instead, the F1 sporting regulations spell out what the stewards expect to see:
- Under a single yellow, the driver should have braked earlier or noticeably reduced speed in that part of the track. Lifting off the throttle for a moment usually satisfies this.
- Under a double yellow, it must be clear the driver has not tried to set a meaningful lap time on that lap. In practice this means abandoning the lap. They don't have to pit, though, because the track might be clear next time round.
The stewards check this with car data, so they can see exactly where a driver lifted, how hard they braked and how their speed compared with their other laps.
Yellow flags in qualifying
In qualifying, a yellow flag can wreck someone's session through no fault of their own. Any driver who passes through a double-yellow sector in qualifying or sprint qualifying has that lap time deleted, even if they did slow down. So if a car crashes late in Q3, everyone still out on a flying lap behind it will usually lose their final attempt.
This sometimes leads to suspicion that a driver crashed or spun on purpose to protect their position. The stewards can and do investigate that, but it is very hard to prove. See how qualifying works for more on the session itself.
Yellow flags during the safety car
When the safety car or virtual safety car is out, all marshal posts show waved yellows along with an "SC" or "VSC" board. If there are also double yellows at the scene of the incident, drivers must slow down even more there, staying above a minimum sector time set by the FIA's control unit in every marshalling sector involved.
Penalties for ignoring yellows
Failing to slow properly is treated seriously, because marshals are often standing near the track when yellows are out. In qualifying, the usual penalty is a drop on the starting grid. At the 2021 Qatar Grand Prix, Max Verstappen got a five-place grid penalty for not slowing for double yellows, and Valtteri Bottas got three places for a single yellow in the same session.
Overtaking under yellows in a race usually brings a time penalty, unless the driver hands the place straight back. See types of penalties.