Thirteen major arterial roads in Melbourne's growing north and south-east will be upgraded in a $2.2 billion project to ease congestion and slash travel times.

Road upgrades — Northern suburbs Sunbury Road

Sunbury Road Craigieburn Road

Craigieburn Road Epping Road

Epping Road Childs Road

Childs Road Bridge Inn Road, Doreen

The Victorian Government said it was the biggest investment in suburban roads in the state's history and would include upgrades in several marginal seats it plans to target in the state election.

Roads Minister Luke Donnellan said the plan included two new bridges over the Cranbourne rail line and another one over Peninsula Link in Seaford.

He said extra lanes would also be built on the Narre-Warren — Cranbourne Road, along with Sunbury, Craigieburn and Epping Roads.

Mr Donnellan said it was about addressing the growth pressures in the north and south-east. ( ABC News: Chris Sonesson )

Road upgrades — South-eastern suburbs Healesville-Koo Wee Rup Road, Pakenham

Healesville-Koo Wee Rup Road, Pakenham Lathams Road, Carrum Downs

Lathams Road, Carrum Downs Narre Warren-Cranbourne Road, Cranbourne

Narre Warren-Cranbourne Road, Cranbourne Pound Road West, Dandenong South

"This is very much about addressing that growth pressure we're seeing both in the north and south-east suburban Melbourne," he said.

"Sure, some of those seats will be Labor seats, some of them won't be Labor seats.

"This is about dealing with the growth that Victoria and Melbourne's going through."

Mr Donnellan made the announcement with Premier Daniel Andrews in Cranbourne.

"This comes on top of a very big boost of $1.8 billion last year for Melbourne's west," Mr Andrews said.

"These unprecedented investments in better suburban roads, so that those roads can work better for local residents, also create some 4,200 jobs."

Expressions of interest will go out to tender toward the end of this year with the winning tenders named in 2019.

It will take about five years to complete the planned upgrades which will be managed by a new agency called the Major Road Projects Authority.

Melbourne is Australia's fastest-growing city with 4.9 million people living in the city. ( ABC News: Joanna Crothers )

'Cynical cash splash'

Melbourne has cemented itself as Australia's fastest-growing city with the highest ever net annual population increase of 125,000 in the 2016-2017 financial year.

There are now 4.9 million Melburnians, and Cranbourne East, in the city's south-east, is the fastest-growing suburb in the country.

There will be "substantial travel time savings" Mr Donnellan said.

"A lot of these roads were built many many years ago. They're not fit for purpose any more," he said.

"In other words they are congested consistently.

"It's very much about getting that journey time down and ensuring people don't get blocked by level crossings."

But the Opposition is cynical about the announcement calling it a "cash splash for votes".

"We've had population growth and traffic congestion for many, many years," Liberal roads spokesman David Hodgett said.

"People are sick and tired of being stuck in traffic and here we have [Premier] Daniel Andrews, seven months before an election, all of a sudden he's realised it's a problem he's going to throw money at this."

Mr Hodgett said while he supported the idea of spending money on road upgrades "let's have a planned, targeted way of doing it".

