Last week the Victorian state government unveiled a plan to build a $50 billion suburban rail loop, if re-elected in November’s state election.

Due for completion in 2050, the Suburban Rail Loop will connect every major Melbourne railway line – proposed stops include Werribee, Sunshine, Melbourne Airport, Broadmeadows, Fawkner, Reservoir, Bundoora, Heidelberg, Doncaster, Box Hill, Burwood, Glen Waverley, Monash, Clayton and Cheltenham. Currently, train users must travel into the Melbourne city to access connecting trains to the city’s outer suburbs.

The loop is being heralded as “the biggest public transport project in Australian history” by the state government, but the secretive build up to the announcement and its proximity to a major election, combined with the scale of the project, has raised questions about its viability.

Following the surprise announcement more details have come to light – and more questions have been raised. Here’s what we know so far.

Design
The new loop will bring Melbourne’s rail network into line with those of London and Tokyo, which have rail lines running around the city as well as towards it. Melbourne’s rail network currently has a radial set up, and all train lines converge on the city centre.

The Suburban Rail Loop will connect Melbourne’s 10 major train lines, with stations at Sunshine, Broadmeadows and Clayton doubling as regional rail interchanges.

Ninety kilometres of track will run underground between Cheltenham and Broadmeadows, with ground-level sections between Melbourne Airport and Werribee.

Five new stations will be built at Melbourne Airport, Bundoora, Doncaster, Burwood and Monash. Commuters will not be able to travel directly into the city from these sites, except for Melbourne Airport.

The loop will connect major health centres Austin Hospital, Monash Medical Centre and Box Hill Hospital, and education hubs Deakin University, Monash University and Box Hill Institute.

The new line is predicted to carry 400,000 passengers a day and take 200,000 cars off major roads. Minister for public transport Jacinta Allan told 3AW there are no plans to include sky rail in the design.

Cost
Right now, the state government says the project is likely to cost $50 billion. Allan told the radio station that contributions from both the federal government and private investors would be required to fund the loop.

On ABC radio, federal Labor leader Bill Shorten said he ''liked the principle'' of the proposal but would not guarantee that, if elected, his government would invest in the project.

Controversy
The first round of strategic planning for the Suburban Rail Loop was put together by Development Victoria, the government agency set up in 2017 to manage Victoria’s major projects and property interests. As reported by the Age, Development Victoria does not have extensive transport expertise. On Tuesday, Premier Daniel Andrews said detailed engineering plans and a business case were yet to be completed.

Some claim the project should have been assessed by Infrastructure Victoria, the body specifically created to provide the government with independent information on the state’s major infrastructure projects. Speaking to the ABC, Infrastructure Victoria CEO Michel Masson said the rail loop had not been considered in its 30-year strategy, which was released in 2016.

As reported by news.com.au, in 2015 Andrews said Infrastructure Victoria was established to “take short-term politics out of infrastructure planning”. Some see the timing of the announcement so close to Victoria’s state elections as a contradiction of Andrews’s earlier statement.

Reception
The Sydney Morning Herald reported the rail loop could “promote a new housing boom” around the 15 stations and “curb growth on the urban fringe”.

Although the project is popular with the general public, others have questioned its viability or if the funds required would be better used elsewhere.

The Grattan Institute's Marion Terrill told the ABC pressing issues such as signal upgrades and line duplications should be a priority. “If you are going to spend $50 billion on this, then you do forgo a lot of other things,” Terrill said.

State opposition politicians were quick to dismiss the project.

“They have no business case, no engineer’s report and they won’t rule out more sky rail across Melbourne,” shadow treasurer Michael O’Brien said in a statement. “They refuse to say how many thousands of homes would be compulsorily acquired.”

Timeline
The state government has estimated the entire project will be completed by 2050. With plans to break ground in 2022, we’re looking at 28 years of construction.

To put things into perspective, the 12-kilometre City Loop took 14 years to complete.

Alesha Printz, Victorian president of Engineers Australia, told the Age the project could be completed in 15 years, but warned speeding up the build would likely increase costs.

More information and project updates can be found at bigbuild.vic.gov.au.