[1] Sydney's suburban rail network is the busiest in Australia, with over 359 million journeys made in the 2017–18 financial year.

Double-deck trailer carriages were delivered to the NSW Government Railways in the 1960s, and incorporated into sets with single-deck power cars.

Freight operators include Crawfords Freightlines, Pacific National, Qube Holdings and SCT Logistics.

[16] The North Shore line opened in 1890 to St Leonards and then in 1893 to a harbour-side station at Milsons Point.

[18] The railway system as it exists today is really the result of the vision and foresight of John Bradfield, one of Australia's most respected and famous civil engineers.

[19] Bradfield's vision for metro-style subways in Sydney was inspired by the metros London and New York City.

[5] Whilst inferior to and more expensive than modern single phase alternating current equipment, it was in vogue during the 1920s, having been used in Melbourne since 1919 and is generally sufficient for the operation of electric multiple unit trains.

However, the introduction of powerful electric locomotives in the 1950s, followed by the Millennium train in 2002, revealed drawbacks in this antiquated system of electrification.

As the voltage is relatively low, high currents are required to supply a given amount of power, which necessitates the use of very heavy duty cabling and substation equipment.

Until the retirement of electric locomotives from freight service in the 1990s, it was often necessary to observe a "power margin" to ensure that substations were not overloaded.

Electrification came to Sydney's suburbs on 9 December 1926 with the first suburban electric service running between Central station and Oatley on the Illawarra line.

[27] In 2020, transport minister Andrew Constance stated that Sydney had become a “train city, it wouldn’t matter if it was light rail, metro or the inter-city trains.”[28] The goods system has also been expanded.

However this separation into a horizontally operated rail system was criticised for the passing of blame for rail delays and accidents between authorities, and in 2004 railways in Sydney became a vertically operated system again with the creation of RailCorp, a fusion of the SRA and the urban sections of the RIC.

In July 2013, RailCorp was reduced to become the owner of the infrastructure and rolling stock, with the service provision that it operated under the CityRail and CountryLink brands transferred to Sydney Trains and NSW TrainLink.

[33][34][35][36] With limited exceptions, all outside of Sydney, trains in New South Wales use standard gauge, with a distance of 1,435 mm (4 ft 8+1⁄2 in) between the rails.

Three of these sections of railway are extensions of suburban main line commuter services, while two are part of a completely segregated metro system.

Central and Circular Quay are above-ground stations (Circular Quay is elevated, directly underneath the Cahill Expressway), while the remainder are below ground, meaning the underground segment of the City Circle consists of two branches, meeting at the approach to Central before surfacing.

Circular Quay remained a "missing link" until 1956, when it connected the ends of the two underground branches via an elevated track.

It runs between Redfern, Central, Town Hall, Martin Place, Kings Cross, Edgecliff, Woollahra (Unused Platforms) and Bondi Junction stations.

At the time of its construction, the line had been intended to finish at Kingsford but it was curtailed at Bondi Junction for political and financial reasons.

Stub tunnels were constructed at the northern end of Epping station in the event that work on the remainder of the line ever resumed.

These stubs were instead used to connect to new tunnels for the Northwest Metro, which opened in 2019, ending the possibility of extending the railway to Parramatta as a commuter rail line.

The fifth underground line is a part of Sydney Metro City & Southwest, with the tunnelled section from Chatswood to Sydenham opening in 2024.

These tunnels, which pass under Sydney Harbour, connect the above ground Metro platforms at Chatswood and Sydenham via underground stations/platforms at Crows Nest, Victoria Cross, Barangaroo, Martin Place, Gadigal, Central, and Waterloo.

Like St James station, the abandoned platforms at Redfern and Central have stub tunnels, although they are much shorter.

A pair of tunnels run underneath Pyrmont and Glebe and are now part of the light rail line.

[44] The third tunnel was created in 2000 when an extension to the City West Link Road through Leichhardt was built on top of a cutting.