Melbourne's traffic congestion is now as bad as Sydney's, new research suggests, and commuters are feeling the pinch as work on Melbourne's Metro Tunnel ramps up.

The Grattan Institute, a Melbourne-based think tank, has released preliminary findings from a report into the city's traffic problems, which said Melbourne's congestion was on par with Sydney's — despite the widespread belief the NSW capital was the country's worst for traffic problems.

"I was a bit surprised," report author Marion Terrill said.

"I had assumed because Sydney was a little bigger, and the harbour makes it so tricky, that Sydney would be in a worse position.

It can take 70 per cent longer to get into Melbourne's CBD during peak times. ( Supplied: Grattan Institute )

"In Melbourne you see more [congestion] in the inner-ring suburbs, whereas in Sydney it seems to be an everywhere, widespread problem.

"So in some ways that may be a more hopeful thing for Melbourne, that the solutions may be more readily available, because if we solve a few key things it may make a substantial difference."

Ms Terrill said the data showed Melbourne's north-eastern suburbs were the worst affected, with a peak-hour trip taking twice as long as it does in the early hours.

"Coming from all compass points you get significant morning and afternoon peaks, where it can take 60 or 70 per cent longer than it would if there was no traffic, but the north-east is a real standout, particularly in the morning," Ms Terrill said said.

The Eastern Freeway and arterial roads around the freeway were a particular problem, she said.

Traffic has been reduced to one lane in each direction on St Kilda Road. ( ABC News: Georgia Spokes )

St Kilda Rd work disrupts traffic

The trip to work could get even worse in the coming weeks as work on the city's $11 billion Metro Tunnel project gets into full swing, with one of the main thoroughfares into the CBD reduced to one lane of traffic in each direction.

The closures along St Kilda Rd are part of the rail tunnel project, which involves the construction of five new inner-city stations. It will continue for the next two weeks.

VicRoads said there had been an increase in congestion around Kings Way during the morning peak, but the school holidays meant traffic across the network was significantly reduced.

Eight tram services will also be disrupted along the St Kilda Rd corridor for the duration of the works.

Unrelated works on suburban and regional train lines are also causing changes to regular timetables.

Evan Tattersall, the CEO of the Melbourne Metro Rail Authority, told ABC Radio Melbourne it would be difficult in the short-term but the new infrastructure may help service the city for the next century.

"There is a significant amount of impact, although I'm told this morning that the buses are running very smoothly and the travel time impact is only a few minutes," he said.

"There is going to be a reasonable level of disruption from this, there's no question about that.

"Everyone needs to understand this is building infrastructure to support Melbourne for the next 50 years, and the way these things work around the world, people will probably still be using this stuff in 100 years from now.

Traffic congestion in Melbourne is centred around the inner suburbs. ( ABC News: Giulio Saggin, file photo )

Tolls, levies 'could ease pressure'

Ms Terrill said there was no silver bullet to fix Melbourne's transport congestion woes — but continually building roads was not the answer.

She said improving public transport, increasing tolls and introducing other costs could help ease pressure, particularly around the CBD.

Last year Victoria's independent infrastructure body suggested charging a new levy on property owners to help pay for future major projects.

Figures from Public Transport Victoria showed 20 per cent of all morning peak-hour Metro trains were overcrowded.

"In the end you can't really build your way out of this," Ms Terrill said.

"Some cities around the world … place a cordon around the centre of the city and say 'if you want to come into that area you pay a charge to come in', so London does that.

"If you make parking more expensive, at the margins some people will think, I'm not going to take my car into the city, so they may look at public transport or other options."