YEARS ago, it might have been strange to think the fortunes of a government could rest on a suburban railway line.
That was before the last Victorian election, when the Frankston train line became a potent symbol of the Brumby government's transport woes: overcrowded carriages, ageing infrastructure, myki cost blowouts.
Labor hardheads call it the Frankston Train Wreck - that fateful polling day in 2010 when voters in the sandbelt seats of Frankston, Carrum, Mordialloc, and Bentleigh helped install the Baillieu government with a cautionary tale: a bad transport system loses votes; the pledge of a good one is a game-changer.
Two years later and the trains might be more reliable, but our congestion problems are far from over.
As The Sunday Age revealed this month, some of the busiest rail lines could soon become so overcrowded passengers will be increasingly left behind during the morning peak, unless construction on an underground city tunnel begins within two years to allow more services.
That's the dire prediction of the government's own business case into the so-called Melbourne Metro rail project, a proposed nine-kilometre tunnel from South Kensington to South Yarra with five new underground stations: Arden, Parkville, CBD North, CBD South and Domain.
Transport boffins reckon that once the project is complete, another 24,000 passengers an hour will be able to use the network. The problem is, time is running out. According to department forecasts, ''significant shortfalls'' - where passenger demand simply outstrips supply - will start in 2015 and worsen each year.
Trains can generally take an average of 798 passengers, but anything above that is known as a ''load breach''. If the projections are right, load breaches could become so severe that by 2020, demand between 7am to 10am will often exceed 1200 passengers. That's a lot of unhappy commuters.
''In the event of no further infrastructure being provided, all corridors except Sandringham will have significant overcrowding in three of the four rolling (peak) hours by 2020,'' the business case documents warn. ''Moreover, it is anticipated that crowding will be so severe on the Werribee, Sunbury and Dandenong lines some passengers will be unable to board the trains in the critical peak hour.''
The idea of a city rail tunnel isn't new: the former Labor government also proposed a similar project (albeit a slightly longer version from Footscray to Caulfield) based on the advice of its then infrastructure guru Sir Rod Eddington.
The trouble is, it needs an estimated $8.5 billion to become a reality, not to mention some political will.
Melbourne Metro might be one of Baillieu's key infrastructure plans, but the government doesn't rate it quite as highly as its ''No. 1'' priority, a $13 billion east-west road connecting the Eastern Freeway to the Western Ring Road. Just as Jeff Kennett had CityLink, or Steve Bracks had the Scoresby Freeway, Baillieu is also banking on a big new road to bolster his major project credentials.
It's a curious thing, particularly given Infrastructure Australia (which advises the federal government on proposals worth funding) has ranked Melbourne Metro at the top of its priority list as one of the nation's most urgently needed projects, while the east-west link was ranked further down as a project with ''real potential''.
The government's thinking goes something like this. First, Melbourne has 4 million people - to not have a ring road connecting the east and west is effectively a productivity killer.
Second, compared with rail, some view that a road project would be easier to finance (through a combination of state/federal surpluses and private sector investment) and also easy to sell (easing traffic congestion; improving freight; boosting jobs).
Third, an east-west road is expected to benefit voters in Victorian seats the Liberals want to either win or retain at next year's federal election, such as Deakin, Chisholm, Aston and Casey. Little wonder Tony Abbott has promised $1.5 billion for the project if he becomes prime minister.
But while a new road has its merits, the public policy benefits of improved rail warrants a rethink of the government's priorities.
The Melbourne Metro might not be a panacea for all our congestion woes, but it has the potential to reshape the network, and get more people using trains.
The proposed tunnel would link the Sunbury rail line to the Dandenong Rail Corridor, with longer trains and extra services in peak hour. The City Loop would in turn be freed up to allow more trains to run on the Frankston, Craigieburn and Upfield lines.
Rail should be at the top of the government's infrastructure list. After all, the last thing Baillieu needs is his own Frankston Train Wreck.
Farrah Tomazin is state politics editor. Twitter: @farrahtomazin