There are currently 275 open stations and over 253 miles (408 km) of active lines, with three million passenger journeys made each day (927 million journeys made 1999-2000; there are a number of stations and tunnels now closed) Lines on the underground can be classified into two types: sub-surface and deep level. The sub-surface lines were dug by the cut-and-cover method, with the tracks running about 5 meters below the surface. Trains on the sub-surface lines have the same loading gauge as British mainline trains. The deep-level or ‘tube’ lines, bared using a tunneling shield, run about 20 meters below the surface (although this varies considerably), with each track running in a separate tunnel lined with cast-iron rings. This tunnel can have a diameter as small as 356m (lift 8.25 in) and the loading gauge is thus considerably smaller than on the sub-surface lines, though the standard gauge track is used. Lines of both types usually emerge onto the surface outside the central area. The exceptions being the Victoria line which is in the tunnel for its entire length save for a maintenance depot, and the Waterloo & city line which, being very short, has no non-central part and no surface line. Each station displays the underground logo containing the station’s name in place of the word ‘Underground’ both at the entrance to the station and repeatedly along the station walls so that they can easily be seen by passengers on arriving trains.