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
South London line South London line The South London line is an Inner London part of the London Overground rail network. The line is run together with the East London line to provide direct services between and . It consists of eight stations, one of which marks the crossover into the East London line network and runs . Most of the line is on high viaduct over other transport infrastructure. Interchanges with the London Underground are at and the closest on its London Overground extension is . The line is in Travelcard Zone 2. From the early 20th century until 2012 a shorter