headway

Partly from Middle English hauedwei, from Old English hēafodweġ (“head-road, main-road”), equivalent to head +‎ way; partly as a shortening of ahead-way, the source of the nautical sense.

headway (countable and uncountable, plural headways)

1. Movement ahead or forward.
2. (nautical) Forward motion, or its rate.
3. (countable, transport) The 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 pre-determined route.
4. (uncountable, figuratively) Progress toward a goal.
5. (countable) The clearance beneath an object, such as an arch, ceiling or bridge; headroom.
6. (coal-mining) A cross-heading.

• make headway

• seaway