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Headway Between Trains Calculator

Work out headway between trains instantly with clear inputs, formula shown and shareable results.

About Headway Between Trains Calculator

With three-aspect signalling a following train needs two clear blocks ahead, so minimum headway is roughly twice the time to traverse a block plus train length, plus signal and route clearing time. That figure converts directly into the maximum trains per hour the line can carry.

Formula

Headway

headway = 2 x (block length + train length) / speed + clearing time; tph = 3600 / headway

Worked example

With the default values below, Headway Between Trains Calculator returns Minimum headway of 114. Change any input above and every figure here is recalculated in your browser.

Inputs used

Block section length
1,200 m
Train length
220 m
Line speed
100 km/h
Signal and route clearing time
12 s

Results

Minimum headway
114 s
Minimum headway
1.90 min
Trains per hour
31.5 tph
Time to clear a block
51.12 s

Step by step

  1. 1Values used
  2. 2Headway
  3. 3Minimum headway= 114 s
  4. 4Minimum headway= 1.90 min
  5. 5Trains per hour= 31.5 tph
  6. 6Time to clear a block= 51.12 s

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.
  • Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.

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

Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.

Frequently Asked Questions

Why two blocks rather than one?

A three-aspect system needs a caution aspect ahead of the danger aspect, so the following train must be at least two blocks behind.

How does moving block help?

ETCS Level 3 replaces fixed blocks with an absolute braking distance behind the train ahead, cutting headway substantially at the same speed.

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