Goes by seniority, 3 tours , all different hours. When you go in, you pick from what is left. AM PM NITE Vacation relief, Lunch Rellief. The further back you are, the less choices you have,My friend retired after 31 years at the end of 2020. You can work anywhere in the system any hour of the day by tour. Vacation Relief you can work any station in the system any tour week by week. Lunch relklief you run around from station to station giving them 1;/2 hour breaks,