, Ealing Broadway, and , relieving overcrowding. History Central London Railway The Central London Railway (CLR) was given permission in 1891 for a tube line between Shepherd's Bush and a station at Cornhill, and the following year an extension to Liverpool Street was authorised, with a station at Bank instead of at Cornhill. The line was built following the streets above rather than running underneath buildings, because purchase of wayleave under private properties would have been expensive, and as a result one line runs above another in places, with platforms at different levels at St Paul's, Chancery Lane and Notting Hill Gate stations. The tunnels were bored with the nominal diameter of , increased on curves, reduced to near to stations. The tunnels generally rise approaching a station, to aid braking, and fall when leaving, to aid acceleration. The Central London Railway was the first underground railway to have the station platforms illuminated electrically. All the platforms were lit by Crompton automatic electric arc lamps, and other station areas by incandescent lamps. Both the City and South London Railway and the Waterloo and City Railway were lit by gas lamps, primarily because the power stations for these lines were designed with no spare capacity to power electric lighting. With the white glazed tiling, all underground Central London Railway platforms were very brightly lit. The use of electric lighting was further made possible because the Central London was also the first tube railway to use AC electrical distribution and the substation transformers were easily able to provide convenient voltages to run the lighting. Earlier tube lines generated DC power at the voltage required to run the trains (500 volts). The line between Shepherd's Bush and Bank was formally opened on 30 June 1900, public services beginning on 30 July. With a uniform fare of 2d the railway became known as the "Twopenny Tube". It was initially operated by electric locomotives hauling carriages, but the locomotive's considerable unsprung weight caused much vibration in the buildings above the line, and the railway rebuilt the locomotives to incorporate geared drives. This allowed higher-speed and lighter motors to be used, which reduced the overall weight of the locomotive as well as the unsprung weight. The railway also tried an alternative approach: it converted four coaches to accommodate motors and control gear. Two of these experimental motor coaches were used in a 6-coach train, the control