A Melbourne airport rail line could be underway by the end of 2022 with the state government matching a $5 billion federal commitment.
Premier Daniel Andrews announced on Sunday that a re-elected Labor government would provide up to $5 billion towards the construction through Sunshine, a line that would connect regional lines to high speed rail.
"We were never going to agree to just an airport rail link, it can be an airport rail link and it can unlock capacity for rapid, fast services to Geelong and Ballarat," he told reporters.
"It's the alignment, it's the corridor option, that stacks up best."
A trip from CBD to the airport should take around 30 minutes.
Assessment of the four preferred routes for the rail line gave the Sunshine option a better performance than going through Flemington, Craigieburn or tunnelling under the Maribyrnong defence site.
According to the strategic appraisal of the Sunshine route, released on Sunday, passengers from Warrnambool, Geelong, Ararat, Maryborough, Ballarat, Swan Hill, Echuca, and Bendigo will get at least 30 minutes cut off their travel times to the airport if they used the train and would no longer have to go into the city to catch the SkyBus.
The detailed business case for the Sunshine route is expected to be completed in 2019/2020.
The cost range is expected to be $8 billion to $13 billion and Mr Andrews said the project could be an opportunity to partner with the private sector.
However, he could not say if that would lead to more expensive tickets for travellers.