headway

plural headways

1. countableuncountableA movement ahead or forward.
2. countableuncountablenauticalForward motion, or its rate.
3. countabletransportThe interval of time or distance between the fronts of two vehicles (e.g. buses) moving in succession in the same direction, especially along the same predetermined route.

   Sixty minutes divided by the headway gives a potential figure for 'trains per hour' - the simplest possible and most simplistic definition of capacity, termed line capacity.

   2019 October, William Barter, “West Coast capacity study”, in Modern Railways, page 66

   1 more example

   The whole of the main lines to be electrified were being equipped with four-aspect colour-light signals, automatically operated, where appropriate, and spaced to give a 5min headway throughout.

   1961 December, “Planning the London Midland main-line electrification”, in Trains Illustrated, page 719

4. figurativelyuncountableProgress toward a goal.
5. countableThe clearance beneath an object, such as an arch, ceiling or bridge; headroom.

   So as not to impede navigation the two principal spans of the bridge were designed to provide a clear headway of 157 ft. above high water for a distance of 500 ft.; [...].

   1941 January, the late John Phillimore, “The Forth Bridge 1890-1940”, in Railway Magazine, page 5

6. countableuncountablebusinessA crossheading.