Work out headway between trains instantly with clear inputs, formula shown and shareable results.
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.
Headway
headway = 2 x (block length + train length) / speed + clearing time; tph = 3600 / headway
Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.
A three-aspect system needs a caution aspect ahead of the danger aspect, so the following train must be at least two blocks behind.
ETCS Level 3 replaces fixed blocks with an absolute braking distance behind the train ahead, cutting headway substantially at the same speed.