An independent infrastructure body has recommended Melbourne join London, Singapore and Stockholm in introducing a congestion tax for motorists using roads in the inner city.

Key points: Infrastructure Victoria's draft strategy includes proposal for congestion tax

Infrastructure Victoria's draft strategy includes proposal for congestion tax Premier Daniel Andrews has ruled out charging fees for existing roads

Premier Daniel Andrews has ruled out charging fees for existing roads Car use in London dropped 20 per cent after congestion fee was introduced

Infrastructure Victoria recommended the measure in its $100 billion draft strategy, which outlined 134 recommendations to support the state over the next three decades.

Premier Daniel Andrews has ruled out fees for the use of existing roads, saying the State Government has a "consistent policy" that would not be changing.

But Infrastructure Victoria chief executive said a tax could reduce the number of trips by 5 per cent, which would reduce traffic as much as school holidays.

How would it work?

The proposal put forward by Infrastructure Victoria looks at a "double cordon" approach, which would see one ring around the CBD and another around the inner suburbs.

Travellers within the city ring would be hit with a $3 fee, while it would be $2 to travel in the inner suburbs.

The modelling showed that would result in reduced cars travelling to the city, and a boost of about 5 per cent in public transport use.

A map shows a proposal for a "double cordon" congestion tax in Melbourne. ( Infrastructure Victoria )

A second proposal suggested a $3 fee to travel into the CBD, and a distance charge of 5 cents per kilometre across the entire network.

But under that scenario, car use dropped more in the outer suburbs than the city, suggesting it would worsen accessibility.

Mr Masson said the organisation was continuing to look at the best options.

"We'll continue to steer the debate and make sure that we engage with the community to try to get out of that situation where we feel that using the car on the road is a freebie," he said.

"It's not — there is already a lot of taxes which are being paid which people are not aware of."

Congestion levies overseas

Congestion levies are used in London, Singapore and Stockholm, and the 30-year strategy looked at how these might be applied in Victoria.

Infrastructure Victoria said the first electronic congestion charging system was introduced in Singapore in 1998, leading to a 16 per cent drop in peak hour traffic by the year 2000.

In London, a congestion charge on private vehicles came into effect in 2003. Car use there decreased by nearly 20 per from 2000 to 2009.

Car traffic in London decreased by 20 per cent after a congestion charge was introduced. ( Reuters: Stefan Wermuth )

But Infrastructure Victoria said the London structure of a flat charge from 7:00am to 6:00pm had been less effective at addressing congestion in peak times.

"Instead, the charge has actually had a more profound impact on reducing private vehicle use between the peak periods [when congestion is less of a problem]," the draft strategy said.

"In addition, the cost of administering the scheme is high [exceeds 50 per cent of total revenue], which reduces the amount of funds that can be spent to improve alternative public transport options in the area, such as buses.

"An alternative, in this case, might be to increase the charge during peak times only."

Mr Masson said the organisation was doing more research on congestion levy modelling and would present its findings later this year.

'Dreamed up at a Fitzroy dinner party'

Opposition Leader Matthew Guy scotched the idea, saying it sounded like something that was dreamed up at a Fitzroy dinner party.

But it has the support of the Grattan Institute's transport program director, Marion Terrill.

"The basic advantage of it is you can't really build your way out of congestion," she told 774 ABC Melbourne.