Work out fleet size for headway instantly with clear inputs, formula shown and shareable results.
The number of vehicles needed to sustain a headway is cycle time divided by headway, rounded up. Cycle time is the round trip running time plus layover, which absorbs delay and gives drivers a break. A spare ratio of ten to twenty percent covers maintenance, inspection and breakdown, and without it the timetable cannot be delivered.
Vehicles in service
In service = ceil(round trip time x (1 + layover) / headway)
Total fleet
Fleet = vehicles in service x (1 + spare ratio)
In service = ceil(round trip time x (1 + layover) / headway). The number of vehicles needed to sustain a headway is cycle time divided by headway, rounded up.
Because a fractional vehicle cannot exist. On a short route, needing 8.1 vehicles means buying nine, so trimming a minute off the round trip can remove a whole vehicle from the capital and operating cost.
This calculator takes 4 inputs: Round trip running time, Target headway, Layover and recovery allowance, Spare vehicle ratio. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.