The Central line is a London Underground service that crosses London from Ealing and Ruislip in the west to Stratford in East London before heading north-east to Epping in Essex, outside Greater London and the M25, London's orbital motorway. Coloured red on the tube map, the line serves 49 stations, 20 of which are below ground, in 46 miles (74 km) and is the longest tube line. One of London's deep-level tube railways, the trains are smaller than those on British main lines.
In terms of total passengers, the Central Line is the busiest line on the London Underground. In the year 2011/12 over 260 million passenger journeys were made on the Central line with 34 trains per hour operating at peak hours making it the busiest and most intensively used railway line in the United Kingdom.
Although the section between Leyton and just south of Loughton is on the surface, it is the oldest rail alignment in use on the current London Underground system, having been opened by the Eastern Counties Railway in 1856, seven years ahead of the Metropolitan Railway.
The line has the shortest escalator on the London Underground system, at Stratford, with a rise of 4.1 metres (13 ft) and also the only station where an escalator takes passengers up to the trains, at Greenford, which is also the only escalator with wooden treads left on the system.
The line has the shallowest Tube platforms on the system, at Redbridge, just 7.9 metres (26 ft) below the road, and the sharpest curve, the Caxton Curve, between Shepherds Bush and White City.