The 288-page business plan confirmed that an underground station would likely be more comfortable for passengers by providing an air-conditioned passage to platforms and the concourse.
But it considered an elevated station would provide more options for connecting to the proposed Suburban Rail Loop, which could be built from Box Hill to the airport around 2050.
Above ground would also cost half as much and shave about 21 months off construction, the business case said.
Bowen said it was also crucial that fares to the airport were affordable for travelers and suggested discounts for people who worked at the airport to encourage patronage.
Allan said fares would be determined closer to the opening date, but the business case was based on assumptions that fares would be comparable to Sydney Airport train station, where it costs $19.53 to board or alight at the gateway in peak times.
The government has also promised to build a new station in Keilor East along the 12 kilometers of new track branching from Sunshine Station, linking 150,000 people in the Moonee Valley area to the Victorian rail network.
The extra stop will add around two minutes to the 30-minute journey time between the CBD and airport. The business case assumes that the Melbourne grows and congestion on the Tullamarine Freeway worsens, driving to the airport from the CBD will take 40 minutes by 2031 and just over an hour by 2051.
The Victorian Auditor-General’s Office on Wednesday said that the airport rail business case may have overstated the project’s benefits and could not support a “fully informed” investment decision because it did not follow government guidelines for calculating economic returns.
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