Circle line (London Underground) with the other London Underground sub-surface lines: the Hammersmith & City line from Hammersmith to just before Aldgate; the Metropolitan line from Baker Street to Aldgate; and the District line from Tower Hill station to Edgware Road station. The line is electrified with a four-rail DC system: a central conductor rail is energised at and a rail outside the running rail at , giving a potential difference of . The running rails are not electrified. Much of the double track railway from the Hammersmith terminus to Westbourne Park station is on a high brick viaduct. East of Westbourne Park the
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