Copenhagen Tunnel

The Copenhagen Tunnel is a railway tunnel in London, United Kingdom, that is situated approximately 0.8 mi (1.3 km) down the East Coast Main Line from London King's Cross railway station. It comprises three twin-track bores, of which only the central and western have been in use since the remodelling of King's Cross in 1977. Passenger trains travel through the slow lines in the western bore at 40 mph (64 km/h) and through the fast lines in the central bore at 60 mph (97 km/h); this speed limit is reduced for other train categories. The tunnel was situated at the end of Thomas Brassey's contract to build the Great Northern Railway between London and Peterborough. It originally comprised only one bore but a second was added in 1877 and a third in 1886. The western bore is elevated above the others to allow the Holloway Flyover to begin immediately after the northern portals, which converts the four tracks into being quadrupled by direction instead of speed heading northbound.

Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).