Every couple of months somebody asks a question about the rules that govern pitting during yellow flag periods and the ensuing restarts. This part of the FAQ will attempt to address that question as completely as possible.

Individual cars are not officially running under caution until they "take the yellow flag" by crossing the start/finish line where the flagman is waving it. After crossing the line, they may not pass other cars, but they may pass as many as possible between the time that the flagman starts waving the flag and the time that they take it. This is called "racing back to the line." Drivers who have just been lapped by the race leader will frequently "get the lap back" by running full bore back to the line while the leader backs off.

When the yellow flag first flies the pits are immediately closed. No car may legally enter the pits when they are closed. The penalty for doing so is to restart at the end of the longest line. Frequently drivers whose cars have been damaged in the incident which caused the caution will ignore the red light/sign/flag at the entrance to pit road and enter the pits anyway, since repairing the car immediately is more important than their restart position.

As stated above, after all of the cars have taken the yellow flag, none may legally pass another car that is still moving (although some leeway is generally permitted for passing heavily damaged cars that are obviously just limping back to the pits). The pace car pulls in front of the race leader and the cars bunch up in the order that they were running on the track.

After one caution lap to gather up the field, the pits are opened to all of the cars running on the lead lap. The penalty for a non-lead lap car entering the pits is again to restart at the end of the longest line. At short tracks with two separate pit roads the pace car will accelerate after dropping off the lead lap cars in the front pits so that the lead lap cars going into the back pits will not be placed at such a distinct disadvantage.

On pit road the cars are of course constrained by the pit road speed limit, which varies from track to track between 35 and 65 mph. The penalty for speeding on the way into the pits is to be held for 15 seconds before being allowed to leave your pit stall. The penalty for speeding on the way out of the pits is to be black flagged and called back into the pits for a "stop and go." These are the same as the green flag rules.

When leaving the pits cars may race to the line at the end of pit road and freely pass other moving cars subject to the speed limit. After crossing the line, they are once again "under yellow" and may not pass. There is a NASCAR official stationed at the end of pit road who is responsible for determining the order in which the cars crossed the line.

It is also this official's responsibility to put up the stop sign when the pace car passes that line. When the stop sign is up no cars may exit pit road. Instead they are held until the field passes. [Note: it was a mistake on the part of this official at Watkins Glen in August of 1995 that brought about the situation where Mark Martin stopped past the exit to pit road in order to let the field go by causing Geoff Bodine to stop short and Rusty Wallace to run into him.]

Often a car which has sustained damage or is otherwise in need of repairs that require more than 20-25 seconds will pit multiple times under caution. Each time the car will leave the pits just before the pace car passes the end line and will race back around the track at high speed and reenter the pits. In this way the repairs may be done without losing a lap.

After exiting the pits, cars rejoin the field at the tail end. Again no passing is allowed under yellow.

One lap after the pits are opened to the lead lap cars, they are opened to all of the remaining cars.

Laps run under yellow still count, and drivers who choose not to pit naturally pass those that do. If all of the cars running on the lead lap pit, any cars running one lap down that do not pit will pass the leader and thus "get their lap back" and be running on the lead lap. However, these cars may not pass the pace car, so when the race leader rejoins the field these cars will be on the "tail end of the lead lap," only a few car lengths ahead of being lapped again.

When the flagman gives the "one to go" signal, the pace car driver turns out the flashing lights on the pace car. The field then splits into two groups (lines). All cars running on the lead lap maintain their order relative to each other in the outside line, while all cars running one or more laps down pull to the inside and form the second line behind the pace car. These lapped cars may now pass as many lead lap cars as necessary but may not pass any of the other lapped cars.

The combined situation of lapped cars starting in a separate line and cars at the tail end of the lead lap starting in front of the race leader sometimes creates a slightly paradoxical situation where one or more cars are starting in the inside line because they were a lap down, but pass the leader and thereby technically get their lap back when forming that inside line because of the "tail end" cars in front of him. Such cars do not however move to the outside line.

The situation on road courses and at any race with less than ten laps to go is that the restart is single file - all drivers line up according to their position on the track after exiting the pits.