Wellington's transport planners are moving to fast-track approval for light rail before the next general election. (File photo)

Light rail could be approved for Wellington within the next two years as part of an almost $4 billion plan to fix the city's traffic congestion problems.

And the mass transit system would not come at the expense of roading projects, with a State Highway 1 tunnel under Te Aro, between second Mt Victoria and Terrace tunnels, also part of the final proposal.

The comprehensive plan, which aims to ease congestion between Wellington Airport and the Ngauranga Gorge, is awaiting sign-off from Cabinet before being released publicly later this year.

SUPPLIED The light rail system could pass through a proposed Mt Albert tunnel portal. (File photo)

It is understood the group behind the project, which would cost between $3b and $4b, is racing to get approval for the light rail system within the current Labour-NZ First term of government, which ends in late 2020.

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The coalition government has promised a greater commitment to public transport funding, including rapid transit, and has already signed off two light rail routes for Auckland.

ROBERT KITCHIN/STUFF Motorists would be not be left out of the plans, with plans to widen the Mt Victoria (pictured) and Terrace tunnels. (File photo)

Transport Minister Phil Twyford, who has previously stated that future-proofing for light rail was an "absolute minimum" for Wellington, said on Friday nothing had yet been agreed on.

"Our Government is working closely with the Wellington City Council and Greater Wellington Regional Council on [the] Let's Get Wellington Moving [project]," he said.

"Light rail is being considered as part of this. We will have more to say about this in coming months."

ROBERT KITCHIN/STUFF The Terrace tunnel would get a fourth lane, and would connect to the Mt Victoria tunnel under Te Aro. (File photo)

But it is understood a recommended programme of investment, with light rail at the forefront, has been put forward by the working group.

The only remaining hurdle is how the project would be funded.

While the recently announced Government Policy Statement on Land Transport did not allocate any funding for the project during the next three years, it is understood there is adequate funding available from the three agencies to get the project started.

KEVIN STENT/STUFF Traffic near the Basin Reserve would be separated, but plans for a bridge appear off the table. (File photo)

About $1b would come from the city and regional councils, with the NZTA to also invest heavily. Other options to make up the shortfall include a regional fuel tax, congestion charging, or road tolls.

The right rail link proposed would operate between Wellington Railway Station and the airport, via Newtown, and could require tunnels under Mt Cook and through Mt Albert.

Cost projections for the project to date have ranged from upwards of $1b. Construction timeframes have not been determined but it would likely take several years.

ROSA WOODS/STUFF Wellington Mayor Justin Lester says he supports modern and improved public transport. (File photo)

Feedback from a survey on four proposals released for public consultation earlier this year showed 63 per cent of the 1334 respondents supported the light rail idea.

That's despite an independent study, completed in 2013, nominating a rapid bus route as the best public transport option between the railway station and Wellington Regional Hospital, ahead of light rail or priority bus lanes.

Wellington Mayor Justin Lester said while nothing had been agreed on, there was strong public support for light rail, and he also liked the idea.

"I'm a strong supporter of improved and modern public transport and light rail needs to be a key consideration."

Light rail is like a tramway, but runs on its own dedicated right-of-way. This means it's not affected by traffic speeds.

WELLINGTON'S TRANSPORT WISH LIST