Two scenarios that could be happening when you see the bus next to yours start to move forward are:
1. The driver of the other bus is preparing to leave the depot: The bus next to yours may be scheduled to depart from the depot at that time. The driver could be starting the engine, adjusting the mirrors, and getting ready to drive the bus out of the depot and onto its designated route.
2. The bus next to yours is being repositioned or relocated: It is possible that the bus is not scheduled to depart immediately but is being moved within the depot for organizational purposes. The bus could be relocated to a different parking spot, maintenance area, or designated area for cleaning or fueling. The movement could be part of the regular operations of the bus depot to ensure the smooth functioning and maintenance of the buses.
These scenarios highlight common activities that can occur in a bus depot, where buses are managed, prepared, and moved as part of their operational routines.