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Fleet Size For Headway Calculator

Work out fleet size for headway instantly with clear inputs, formula shown and shareable results.

About Fleet Size For Headway Calculator

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.

Formulas

Vehicles in service

In service = ceil(round trip time x (1 + layover) / headway)

Total fleet

Fleet = vehicles in service x (1 + spare ratio)

Worked example

With the default values below, Fleet Size For Headway Calculator returns Total fleet required of 17. Change any input above and every figure here is recalculated in your browser.

Inputs used

Round trip running timeminimum 1 min
60 min
Target headwayminimum 0.5 min
5 min
Layover and recovery allowanceaccepts 0–40 %
10 %
Spare vehicle ratioaccepts 0–40 %
15 %

Results

Total fleet required
17 vehicles
Vehicles in service
14
Cycle time including layover
66.00 min
Spare vehicles
3

Step by step

  1. 1Values used
  2. 2Vehicles in service
  3. 3Total fleet
  4. 4Total fleet required= 17 vehicles
  5. 5Vehicles in service= 14
  6. 6Cycle time including layover= 66.00 min
  7. 7Spare vehicles= 3

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Fleet Size For Headway figure worked out?

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.

Why does rounding up matter so much?

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.

What values do I need to enter?

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.

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