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 Rail to Enfield Town, Cheshunt and Chingford and Romford to Upminster Line services on 31 May 2015. London Rail London Rail is a directorate of Transport for London (TfL), involved in the relationship with the National Rail network within Greater London, UK which manages TfL's non-London Underground train services. London Rail manages the London Overground (LO), London Trams and Docklands Light Railway (DLR). It will also be responsible for Crossrail. As part of an internal restructure within TfL, it recently merged with the (previously separate) London Underground directorate, bringing all of Greater London local transport services on rails under one division.