The term for the time interval between buses on the same route is headway.
In transit planning, headway measures the spacing between successive vehicles, usually from the front of one bus to the front of the next. A 10-minute headway means a bus is scheduled every 10 minutes, although actual gaps can vary because of traffic, boarding delays, or bunching.
Headway is not the same as running time, which is how long a vehicle takes to travel its route. A layover is scheduled recovery time at a terminus, while dwell time is the period a bus spends stopped to load passengers, unload them, or wait for a signal.
Transit agencies use headway to plan fleet requirements and passenger capacity. Shorter headways generally mean more frequent service and shorter waits, while longer headways may reduce operating costs but make each missed bus more consequential. The term is also used for trains, aircraft, and road vehicles.