Central line (London Underground) that the transport benefits of a Park Royal station on the Central line are not sufficiently high to justify the costs of construction. Central line (London Underground) The Central line is a London Underground line that runs through central London, from , Essex, in the north-east to and in the west. Coloured red on the Tube map, the line serves 49 stations over , which makes it the longest Tube line. It is also one of only two lines on the Underground network to cross the Greater London boundary, the other being the Metropolitan line. One of London's deep-level railways,
London Underground infrastructure London Overground – at New Cross and New Cross Gate. Of the boroughs that the Underground passes through, Hackney is served solely by Manor House station on the Piccadilly line in the very north-western edge of the borough. For the most part however some of the tube lines like the Central line skirt around the edge of the Hackney rather than going through it. Greenwich borough was unserved until North Greenwich station opened on the Jubilee line extension in 1999. The lines are electrified with a four-rail DC system: a conductor rail between the rails is energised at −210 V