 NASCAR uses both a light at the end of pit road and a series of cameras to help determine the moment pit road is closed.The pits are opened once the field is under control of the pace/safety car unless there is an accident near the entrance/exit or on pit road, in which case the pits will remain closed until NASCAR deems the pits are safe to open.After an incident at the June 2015 Chicagoland Xfinity race where the pit flagman waved a green flag but the light at the end of pit road was red, NASCAR added a light to the rear of the pace/safety car to help inform drivers and teams when pit road will be open, and thus removed the flagman from the entrance of pit road.