Tunnel
An underground passage made for traffic This article is about underground passages. For other uses, see Tunnel (disambiguation). "Underpass" redirects here. For the John Foxx song, see Underpass (song). For a tunnel for pedestrians, see Pedestrian underpass. Tunnel in Fort de Mutzig, France Decorated entrance to a road tunnel in Guanajuato, Mexico Utility tunnel for heating pipes between Rigshospitalet and Amagerværket in Copenhagen, Denmark Tunnel on the Taipei Metro in Taiwan Southern portal of the 421 m long (1,381 ft) Chirk canal tunnel A tunnel is an underground passageway, dug through the surrounding soil/earth/rock and enclosed except for entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usual