City Circle

The City Circle is an underground passenger railway line located in the central business district of Sydney. The lines are owned by RailCorp, a government agency of the state of New South Wales. Despite its name, the City Circle is of a horseshoe shape, with trains operating in a U-shaped pattern. The constituent stations of the Circle are (clockwise): Central, Town Hall, Wynyard, Circular Quay, St James, Museum and back to Central.

History
The original concept for the City Railway was part of a report dated 1915 submitted to the government by John Bradfield upon his return from overseas study, with work commencing the following year. The City Circle was built in stages. The first stations to open were St. James and Museum, in 1926, as part of the initial electrification of Sydney railways. Next was the "western limb" through Town Hall and Wynyard, which opened in 1932, in conjunction with the opening of the Sydney Harbour Bridge. This section contains four tunnels. Two connected to the Harbour Bridge, while the two City Circle tunnels terminated at Wynyard. In 1956 the dead ends at St. James and Wynyard were joined and the "missing link" – Circular Quay – was opened. Central and Circular Quay are above-ground stations (Circular Quay is elevated, directly underneath the Cahill Expressway), while the remainder are below ground. Several unused railway tunnels also exist. The former tram tunnels at Wynyard, and other stub tunnels at St James are well known.

Description
The core part of the City Circle consists of two tracks, known as the City Inner and City Outer. As their names suggest, the first is the inner track in the loop and the second is the outer track. The inner track is used in the anti-clockwise direction, while the outer track is used in the clockwise direction. As the line has sharp turns and runs close to building foundations, trains are limited to 40km/h through the City Circle, with a further restriction to 30km/h near the Goulburn St tunnel portals. Empty trains are limited to 10km/h at the start of a platform, then 15km/h until the end of the platform, so that track workers have adequate warning that a train is approaching.

There are no crossovers on the City Circle, so in case a train breaks down, the drivers of the following trains must change ends and drive against the normal running direction to the crossovers north of Central. Because this is dangerous, trains may not exceed 10km/h when performing this move.

There are also other tunnels at Wynyard and Town Hall (for the T1/4/9 lines), however these normally are not considered part of the City Cricle.

Services
The City Circle is normally used as a terminus for trains. Trains enter the City Circle at Central and then go around the loop, emerging again at Central to start their next service. Trains may remain on the same line throughout the loop or emerge on a different line. This table shows how trains use the City Circle: Prior to the integration of the Eastern Suburbs line into the Illawarra Line in 1980, Illawarra line trains (now numbered T4) also operated around the City Circle.

There are also other lines that pass through City Circle stations, but do not use the City Circle tracks:
 * Central and Town Hall only:
 * Central, Town Hall and Wynyard only:
 * Central, Town Hall and Wynyard only:
 * Central, Town Hall and Wynyard only:

Trackwork occasionally closes either one or both tracks of the City Circle. As the line is largely underground with little ventilation, an 86 class electric locomotive (owned by Sydney Electric Train Society) is often used to haul rail into the tunnels. Unlike the rest of the network, trackwork buses are usually not organised for these shutdowns, as it is often easier to walk, take the City & Southeast light rail or the T1/4 train lines.

Stations

 * Central
 * Town Hall
 * Wynyard
 * Circular Quay
 * St James
 * Museum