Orbital rapid transit line under construction in Melbourne, Australia
The Suburban Rail Loop (SRL) is an automated rapid transit system under construction in Melbourne, Victoria, Australia. The system is divided into four distinct sections. The two main sections, SRL East and SRL North, would eventually together form a single fully automated orbital metro line through the city's middle suburbs, with 13 stations between Cheltenham and Melbourne Airport connecting to eight existing Melbourne rail lines. 
The first section, SRL East, is a underground link from Cheltenham to Box Hill via Monash University. Construction commenced in 2022 and is expected to open in 2035.
The second section, SRL North, will be a underground extension of SRL East from Box Hill to Melbourne Airport, via La Trobe University. Construction is not expected to commence until the 2030s, with completion by 2053. This section may be split into two projects due to its length and cost.
The third section, SRL Airport, will be formed by the separate Melbourne Airport Rail project. This section will run from Melbourne Airport via Sunshine into the central business district via the Metro Tunnel. Early construction commenced in 2023 before significant funding delays pushed the opening date out to at least 2033.
The fourth and final section, SRL West, has not been defined in detail but would connect the city's outer western suburbs and may be formed by electrifying the existing Deer Park–West Werribee railway line from Sunshine and extending it to Werribee station. No timeframe for construction has been released.
Melbourne will be the second Australian city (after Sydney) to build a fully-fledged rapid transit system. Several orbital rail schemes have been proposed and some constructed throughout Melbourne's history, but the rail network has remained largely radial. The Victorian Labor state government led by then Premier Daniel Andrews announced the SRL as policy in the lead up to the 2018 state election. Initial planning for the SRL was carried out in secret prior to its announcement, and, when the plans were released, it received significant attention. The SRL plan has been praised for its long-term vision and ambition, as well as being an innovative solution to the difficulties faced by Melbourne's transport network, but is criticised for its political motives, transparency of business case, prioritisation ahead of other transport projects, and large cost.
Although the Victorian government signed the first $3.6 billion contract with the Suburban Connect consortium in December 2023 to build the tunnels, the state Liberal/National opposition remains opposed to the system. Opposition Leader Brad Battin announced in January 2025 that he would halt further development of the SRL if elected.
Background.
The Melbourne transport network was substantially developed in the late 19th century, when the newly available technology of the railway enabled population growth away from the city centre. The result was the development of a largely radial network, which, over the following century, reinforced a model of urban development focused on heavy daily commuter flows into and out of the CBD. Furthermore, a program of freeway construction in the wake of the 1969 Melbourne Transportation Plan reinforced the structure of the suburbs and introduced car dependence to new regions of development not served by the legacy rail network. As a consequence, Melbourne, unlike many cities of comparable size, did not develop any major centres of employment or dense population in its outlying regions over the course of the 20th century.
A number of orbital lines were constructed at the peak of railway development, but most failed to attract the necessary traffic of passengers and goods to remain sustainable into the late 20th century. The Outer Circle, which ran from Oakleigh on the Dandenong line to Fairfield on the Hurstbridge line via the Glen Waverley and Lilydale lines, was constructed between 1888 and 1891 but closed by 1897, though it was partly reopened as the Alamein branch line. The Inner Circle linking the modern-day Upfield and Mernda lines, was opened in 1888 but closed to passengers in 1941. The Albion-Jacana line and Newport-Sunshine line in the city's west, though performing a similar purpose, were never intended to carry passenger traffic.
In the late 20th century, interest grew in enabling orbital journeys between Melbourne suburbs. Included in the 1969 Plan were a number of orbital freeways, some of which were constructed over the following decades. The M80 Ring Road through the outer western and northern suburbs was constructed in stages between 1989 and 1999, and, by the time of its completion, was claimed by its advocates to have been partly responsible for a massive economic boom in the western suburbs, centred on its points of intersection with existing radial routes. EastLink, a similar orbital freeway through the eastern suburbs, opened in 2008, but was less successful, failing to reduce traffic meaningfully on parallel arterials such as Springvale Road. Detailed plans for the North East Link, connecting the Ring Road and EastLink to complete the orbital route, were released in 2018, with construction expected to start in 2020 for an anticipated completion date of 2027.
Despite the investment in orbital road transport from 1990, little changed in the structure of the public transport network. No new suburban railway lines were built after 1930, and trams were increasingly delayed by traffic congestion on key routes. From 2002, the SmartBus program introduced three orbital bus routes in an attempt to meet the city's burgeoning need for outer suburban public transport. In addition to serving new corridors previously without mass transit, the buses were operated at a relatively high frequency and along direct routes, in contrast to the existing network of infrequent and circuitous routes. As a result, the SmartBus routes became the most heavily used in Melbourne, and were widely praised as a model for recasting the future public transport network.
History.
Proposal.
In August 2018, three months prior to the 2018 Victorian state election, then Premier Daniel Andrews promised that a re-elected Labor government would undertake "the biggest public transport building program in Australian history", in a speech to the Committee for Economic Development of Australia. The comments were interpreted as a hint that as-yet-unannounced projects would be revealed closer to the election, although Andrews provided no detail in his speech.
On 27 August, Andrews revealed plans for the Suburban Rail Loop for the first time: a orbital line for Melbourne's rail network, connecting 11 of the city's existing rail lines and serving new regions of the middle and outer suburbs at an estimated cost of $50 billion. The government committed $300 million to complete a business case and feasibility study should it be re-elected, noting that the project would take several terms of government to complete.
In the days following the proposal, the government revealed that its plan had been under consideration within Development Victoria, a planning agency under the Department of Environment, Land, Water and Planning for 12 months. Controversially, neither Infrastructure Victoria nor Transport for Victoria, both established by the Andrews government, had been involved in the SRL's planning stages; furthermore, neither agency had identified the need for a similar project in their long-term plans for the transport network. Andrews defended the decision to develop the SRL independently of infrastructure authorities, arguing that while Infrastructure Victoria "have lots of good ideas, they don't have every good idea".
The tender process for the Melbourne Airport rail link project was launched in mid-September, and the state government confirmed that it anticipated the airport link would form part of the SRL West, with construction beginning in 2022.
In mid-October, Labor federal Leader of the Opposition Bill Shorten announced support for the SRL, including a commitment for $300 million in initial federal funding should the Labor Party be elected. The state government also indicated that it would be prepared to add additional stops to the loop to those included in the original announcement, particularly in the western suburbs.
Days later, a leaked document from Transport for Victoria showed that the SRL had not been included in the transport authority's long-term plan for the rail network.
Planning.
$300 million was allocated to planning works for the SRL in the 2019 state budget. Rail Projects Victoria announced registrations of interest for potential contractors were open in June, and the first geotechnical investigations began in July in Box Hill.
The state government announced the formation of a Suburban Rail Loop Authority in September, at the same time as confirming station precincts for SRL East. In November 2019, the government announced that the loop would be an operationally independent, standalone line using different rail technology from the existing suburban rail network. The system would use new, smaller metro rollingstock that is four to five carriages long, allowing shorter platforms. The Premier announced an intention to use private investment to help fund the line, but did not indicate whether the line would be driverless.
In 2020, the government committed a further $2.2 billion for initial and early works on the loop, with expressions of interest opened for contractors to deliver these works. Jacinta Allan, who in her role as Minister for Transport Infrastructure had overseen the SRL since its inception, was given the additional role of Minister for the Suburban Rail Loop.
Release of Business and Investment Case.
The Business and Investment Case of SRL was released in August 2021, primarily focusing on SRL East and North. SRL East will commence building in 2022 and is expected to finish by 2035. The rail line will be fully underground between Cheltenham and the Airport, while SRL West is subject to further investigation, planning and development.
The business case modelled two staging scenarios. The first scenario has SRL North opening in two sections, the first from Box Hill to Reservoir opening in 2043 and the second between Reservoir and the Airport opening in 2053. This scenario has estimated capital costs of $24.1 to $40.2 billion and total costs of $30.7 to $50.5 billion, with estimated benefits of $48.5 to $58.7 billion. The second scenario is faster but higher cost and has the section from Box Hill to Reservoir opening by 2038 and the full SRL North corridor from Box Hill to the Airport opening by 2043. This scenario had capital costs of $27.1 to $45.1 billion, total costs of $35.1 to $57.6 billion and benefits of $54.7 to $65.8 billion. The timing and cost would be further refined through the tender and planning process. This gave the project a cost-benefit ratio range between 1.0 and 1.7.
The government stated that it expected $30 to $34.5 billion would be spent on the project over the 14 years to the opening of the first stage in 2035, with significant works on SRL North taking place as part of that expenditure.
An Environmental Effects Statement (EES) process for SRL East was initiated in late 2021 that provided more detail on the station locations, the precinct designs, the local effects of the project and the design of the train system. Community and stakeholder consultation was launched as part of this process.
In October 2021, the Minister for Transport Infrastructure Jacinta Allan introduced legislation to the Victorian Parliament to establish the Suburban Rail Loop Authority as a statutory government body and grant it a number of transport and planning powers.
SRL East and North will take more than 25 years to construct and together are estimated by the project's business case to cost between $30.7 and $57.6 billion depending on project staging, of which capital costs would be between $24.1 and $45.1 billion. SRL East and North will be built entirely underground along new rail alignments, while SRL Airport will be formed by the at-grade and elevated Melbourne Airport rail link and funded separately.
Under construction.
SRL East.
The first stage will connect Melbourne's eastern and south-eastern suburbs, including twin underground tunnels from Cheltenham to Box Hill via Monash University. Construction commenced in 2022 and is expected to open in 2035. Passengers will be able to interchange with the existing metropolitan rail network at Cheltenham, Clayton, Glen Waverley and Box Hill. Construction on SRL East began in mid 2022 and the first services are scheduled to start in 2035.
In August 2023, a preferred bidder was announced for the first package of of SRL East tunnels between Cheltenham and Glen Waverley. The Suburban Connect consortium consisted of the Australian construction firm CPB Contractors, Italian civil engineering company Ghella and the Spanish construction company Acciona.
Proposed extensions.
The SRL will ultimately consist of four sections. SRL East and SRL North will form one continuous metro line