A pit stop allows NASCAR drivers to get fresh tires and refuel their cars, all in less than 15 seconds. Drivers may pit for a variety of reasons – worn tires, low fuel, general strategy – and in a variety of conditions.

Caution flags tend to send drivers into pit road; pit stops under green-flag racing rely on precious milliseconds, which often have a big impact on the final race results.

When a driver stops in his pit stall, a six-member crew gets to work on their assigned tasks.

Two of those six workers are tire carries – they carry the 24-pound Goodyear tires to the proper spot and hand them to the tire changers. The two tire changers use an air-powered impact wrench to loosen and discard the old tires before adding the new ones.

Those four members work in pairs (on the back and the front) and handle the right side of the car first.

Tires are able to be changed quickly due to the jackman, who operates a 20-pound hydraulic jack to quickly raise the right side of the car. When the right side has new tires, he quickly lowers the car before repeating the process on the left side. The final member is the gas man, who empties two 12-gallon cans of fuel into the tank. Each can weighs more than 80 pounds.

At the discretion of NASCAR, sometimes a seventh “extra man” is allowed over the wall to clean the windshield and assist the driver. Running this delicate process is the crew chief, who coordinates when to pit and delegates responsibilities prior to the race.

While 15 seconds is the outer reaches of what is considered an acceptable pit stop time, 13 seconds is on the fast side. For safety reasons, drivers are penalized if they are timed speeding in or out of pit road.