dive-under

dive-under (plural dive-unders)

(rail transport) A railway junction where at least one track passes under other lines instead of crossing them on the same level, in order to avoid conflicting movements; an underpass.
- 2019 November 20, “Government delays Heathrow rail to consider other modes”, in Rail, page 25:
  Services from Heathrow would use the existing Byfleet Junction, enabling trains to join the slow line of the South Western Main Line to Woking. The junction already has a dive-under.

railway junction where at least one track passes under other lines

English