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
Central line (London Underground) Crossrail 2 line, running from south-west to north-east London and due to open by 2030, was planned for a number of years to take over the Epping branch of the Central line between Leytonstone and Epping. As of 2013 the preferred route options for the line no longer include this proposal. The Central line runs directly below Shoreditch High Street station and an interchange has been desired locally since it opened in 2010. The station would lie between Liverpool Street and Bethnal Green, one of the longest gaps between stations in inner London. Although there would be benefits to this