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
Suicide on the London Underground rushes on overhead". A study of 58 cases showed that the presence of a suicide pit halved the number of deaths. Another safety mechanism are platform edge doors (PEDs), which separate the train from the passengers. These are installed exclusively at the below-ground stations of the Jubilee Line Extension. PEDs are expensive to install and can fail to open, adding a potential reliability problem to train services. Alison Wertheimer wrote in 2001 that there were 100–150 suicides annually on the Underground. The annual number of suicides in the 1940s was 25, increasing to 100 by the 1980s, which, according to