A decade-long roads building binge has squandered much of the money on pork-barrelling in Australia's marginal regional electorates while cities have been a secondary priority.

Many of the billion-dollar projects selected for state and federal funding have lacked adequate justification or scrutiny, according to a damning new analysis by the Grattan Institute of the last 10 years of infrastructure funding.

By analysing the expense of major road and rail projects against the level of demand, the institute has uncovered the nation's least justified projects, including several rural highways.

The road between Perth and Bunbury is named as the nation's worst-value regional route, having cost the taxpayer over the past decade $18.90 for each car that travelled its 135 kilometres.

Construction of the Perth-to-Bunbury highway Photo: Southern Gateway Alliance

Victoria's Geelong-to-Colac highway duplication, which traverses key swing federal and state seats, was identified as Australia's second biggest waste of money.

The project, according to VicRoads' own description, returned just 8 cents for every $1 spent on it. The upgrading of that highway over the past decade has been so lavish that every car that travelled its length cost taxpayers $12.20.

A VicRoads spokesman said sections of the highway had seen 32 crashes betwen 2008 and 2012, including three fatalities.

Victoria has simultaneously missed out on badly needed infrastructure, the report finds, because of its small number of swing seats. But Queensland and New South Wales, where several seats are critical to winning federal elections, have done well.

In Queensland, the Commonwealth spent 46 per cent more on transport infrastructure than in Victoria, the report finds.

More money was spent in the decade to 2015 on transport infrastructure than at any time since Australian records were kept.

Last financial year alone, Australian governments spent on $19.3 billion on transport infrastructure – $4.4 billion in federal tied grants to states, $1.1 billion from the Commonwealth directly to councils, and individual states $13.8 billion.

But despite the unprecedented funds invested, "it would be difficult to argue that they have spent wisely", says Grattan Institute transport program director Marion Terrill. "Sometimes the decision to proceed with a project came before an assessment of whether it was worthwhile, and sometimes projects that were not worthwhile went ahead anyway."

There was little evidence of any consistently applied methodology for deciding what to fund. Infrastructure advisory bodies set up by federal and state governments have failed to protect the public from projects that, while popular with voters, do not serve the economy.

Despite the existence of infrastructure advisory boards at state level since 2011, the report finds that more than half the federal money spent was "on projects that do not have a published project evaluation".

In Victoria, the East West Link was never assessed before being given $1.5 billion in federal funding.

An artist's impression of stage one of the East West Link.

And its replacement project, Transurban's proposed Western Distributor, will not be assessed by Infrastructure Victoria because the organisation was set up too late by the Andrews government to review the project.

The nation's capitals, where most GDP growth has been concentrated even during the mining boom, are missing out infrastructure funding, the report finds.

Instead of concentrating new investment in Sydney, Melbourne, Brisbane and Perth – which account for 60 per cent of economic activity – Commonwealth and state governments spent disproportionately in country NSW and Queensland.

Only 43 per cent of new investment in road and rail infrastructure has been spent in our four largest cities, it finds, despite their crucial importance to the economy.

The way Australian governments assess transport projects too often relies on secret assessments or "commercial-in-confidence" agreements.

It has left the public unconfident funds are being spent wisely, the report finds.

Complete transparency is needed on all projects if they are to be eligible for federal or state funding, the report says.

"Promising projects on the basis of 'back-of-the-envelope' costings should not be the default mechanism of transport infrastructure planning," it finds. "There are still many examples around the country of politicians making promises in election campaigns or committing to projects on the basis of a poor-quality business case or no business case at all."

Politicising infrastructure funding is more obvious now that so much money is being spent, but the Grattan Institute's researchers concede that pork barrelling is certainly not new in Australia.

Bert Kelly, the former member for the South Australian seat of Wakefield, said in 1961: "I tried to point this out to the government before they committed themselves to building the big dam on the Ord, but there was an election looming and at each election I can feel a dam coming on."

Picture of new overpass being built, New England Highway, Maitland.  Photo: Jonathan Carroll.