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."

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.

Public Transport Minister Jacinta Allan said it's expected the travel time from the CBD would be about 30 minutes, but the business case would confirm that.

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.

Prime Minister Malcolm Turnbull says he is happy with the announcement.

"I have had a number of very good meetings with the Premier, Daniel Andrews, and I'm delighted that today he has confirmed that Victoria will commit the same amount of money, and I'm confident that ... $10 billion will enable us together to build the rail line from Melbourne to Tullamarine airport," he told reporters on Sunday.

Lorie Argus, chief of parking and ground access for Melbourne Airport said the two governments' announcements showed airport rail was "high on the agenda".

"We just know that airports need rail links and it's a critical part of the passenger journey," she told reporters.

Ms Argus said the airport expected the rail option to be "competitive" with SkyBus, which is about $19 one way, and for the two services to co-exist to maximise passenger options.

Opposition Leader Matthew Guy said if his side was successful at the November election, it too would get moving on the project.

"I give that commitment that the federal government's money in the first instance would be used to commence construction of an airport rail," he told reporters.

Australian Associated Press