An announcement is due today on the proposed Let's Get Wellington Moving (LGWM) package.
The long-awaited project is aimed at easing the city's congestion problems, with options such as duplicating the Terrace Tunnel and moving the Inner City Bypass underground floated as potential fixes.
Without further investment in the city's transport system, it's estimated travel times by car and public transport could be up to 25 per cent longer by 2026 and the cost of congestion to the economy up as much as 50 per cent.
More than 2000 people and 50 stakeholder groups took part in consultation for LGWM. From that feedback, Scenario D, the most ambitious, was the most popular.
That scenario included the duplication of both the Mt Victoria and Terrace tunnels, a fourth southbound lane between Ngauranga and Aotea Quay, moving the Inner City Bypass underground and allowing for a mass transit corridor.
Scenario D would take more than 10 years to build and could cost as much as $2.3 billion.
"The recommended programme is unlikely to be one of the four scenarios as presented. It will include parts of the scenarios, as well as other elements supported by the public feedback and our ongoing work," LGWM programme director Barry Mein said in a press release at the time the feedback summary was released.
Announcements on mass public transport, bus and cycle lanes are also expected today.
The announcement has been pushed back more than once after a proposal was meant to be made in August last year.
The drawn-out process was earlier described as "constipated" by Greater Wellington Regional Councillor Ian McKinnon.
Once the decision is released, the city and regional councils will have to endorse the proposal and then work out the practicalities, Councillor Daran Ponter said last week.
"We are probably some years away before we even see the soil being turned on some of these significant projects.
"So it has been a frustrating point to date but we're not out of the woods by any length in the near future."
LGWM is a joint initiative between Wellington City Council, Greater Wellington Regional Council and the NZ Transport Agency.