Have they been a success – economically and in attracting passengers? Both airport rail links in Sydney and Brisbane initially struggled to attract commuters and turn a profit. Early patronage was well below expectation. In Sydney prices were made more attractive with government assistance and demand has grown. Patronage on Brisbane's Airtrain has also grown with millions of commuters now using the airport rail links annually in both cites. Both rail links now turn modest profits. What work has been done on developing a rail passage to Tullamarine. How would it work? How long would it take? Melburnians talk about a rail link to the airport like they do the weather. It has been a constant topic of conversation for decades. The Napthine government has settled on an Albion East alignment that follows the Sunbury line out of the city and takes the Albion-Jacana freight line path. Closer to the airport the rail line will go up the centre of the new Airport Drive freeway extension. The airport is considering three locations for the new train station and hopes to have a final design in 18 months. An underground station has been ruled out because of cost. The airport said there was no "secret Harry Potter platform" already built at the airport, which has been a long-held Melbourne myth. The airport said a future train terminal would not be in current long-term car park areas.

The journey time to the airport is forecast to be an ambitious 25 minutes. What's the government's position? The Coalition said the $8.5 billion to $11 billion Melbourne Rail Link, which includes the airport rail link, would "transform the rail network, reduce delays, improve reliability and boost capacity by up to 30 per cent". It said "early works" were expected in 2016, with construction from 2017 and the full project, including Melbourne Airport Rail Link, to be complete in 2026. The government could not say which section of the Melbourne Rail Link would be built first, the link to the airport or the rail tunnel from Southern Cross to Fishermans Bend and South Yarra. It said exact timing for the opening of both sections of the project would be determined once further design and construction planning had occurred. The budget papers said the project will be completed "from 2026" and contain only 2 per cent of funding in the next three years. And Labor?

Labor said while an airport rail link is a worthy project, it was focused on "the services that people use every single day". It is prioritising building the Melbourne Metro project to increase capacity in the city loop and its plan to remove 50 level crossings. What about the Greens? The Greens support an airport rail link. Where do the key business groups and unions line up – and why? The Victorian Employers' Chamber of Commerce and Industry supports the airport rail link as critical to tourism growth.

Trades Hall said while it supported more infrastructure jobs in Victoria it was not convinced the airport rail project would get off the ground. Trades Hall wants an infrastructure pipeline that focuses on people getting to work and prioritises local jobs. What's the case against – and who makes it? Why duplicate? The Skybus service already runs a direct, frequent and affordable link from the CBD to the airport. Other transport projects will be delayed or cancelled to build a rail line to the airport. As recently as 2011, then Transport Department secretary Jim Betts said about a rail link to the airport "unlike the CBD of Melbourne, which has repeat concentrated flows ... you don't have that base load of commuter demand that justifies railways in other circumstances". Some consider an airport rail link a white elephant that would not suit the travel habits of many airport visitors. The new airport rail link plan from the Coalition would also mean the Metro Rail plan to expand capacity in the city loop with a tunnel from South Kensington to South Yarra and with five new stations at Arden, Parkville, CBD North, CBD South and Domain would be scrapped. Metro Rail was years in the planning and was supported by Infrastructure Australia. Can projects like this ever be considered an economic success – and should they be considered in economic terms alone? Brisbane and Sydney rail lines are profitable. The economic benefits of a rail link would grow as congestion worsens on the Tullamarine Freeway. Visitors to Melbourne Airport are expected to double in the next three decades and hit 60 million a year by 2030. The airport says the rail link is desperately needed to cope with anticipated demand.

If not, what else should we be looking at? If not airport rail, what's the alternative? Some have suggested an elevated light rail system running above CityLink as a less expensive, faster and more convenient rail alternative. At the minimum, the SkyBus service to the airport should have a dedicated CityLink lane to avoid getting stuck in congestion.