The Government will pay the "lion's share" for a $15 billion light rail line from the city centre to the airport in Auckland and is confident of having it built by 2033.
Finance Minister Grant Robertson and Transport Minister Michael Wood gave those assurances when announcing the Government's preferred option for light rail today.
The ministers also announced they are bringing forward planning for a second Waitematā Harbour crossing with public consultation on options starting this year, with a preferred option selected in 2023.
This will include choosing a route, deciding on tunnels or another bridge, and confirming what transport modes will be able to use the crossing.
Light rail will run in tunnels all the way from Wynyard Quarter to Mt Roskill, roughly following the route of Sandringham Rd, although there is flexibility around the route.
It will then proceed on a surface track alongside State Highway 20, deviating to stop at Onehunga and Māngere townships before continuing to the airport.
The new line, known as City Centre to Māngere (CC2M), will have about 18 stations, with trains running every five minutes.
It will be capable of carrying 12,000 people per hour, which the Government says is four times more passengers than can be carried on a dedicated busway or "trackless trams".
The ministers said the "hybrid" system had been chosen over two other options - light rail at street level costing $9b and light metro above or below ground costing $16.3b. This is because it had greater carrying capacity, was less disruptive and better aligned to a linked-up rapid transit transport network, they said.
The three options were prepared by a light rail establishment unit and presented to the Government in October.
Robertson, who has the job of rustling up $15b for the project, said it would be easy to go with the cheaper option, but he had become convinced the preferred option from the establishment group better met the needs for an integrated rapid transit plan.
He said the Government will fund the "lion's share" of the $15b project and look at other options, including "value uplift" - a charge on businesses and developments that benefit from the project - and some kind of targeted rate.
Whether the targeted rate will be set and collected by Auckland Council has still to be determined.
Mayor Phil Goff said the council would have a role to play providing infrastructure around the project as part of plans to build 66,000 new homes and create 97,000 new jobs by 2051.
But he said given the council's current financial position, it does not have the capacity out of rates to pay for light rail, saying Aucklanders will contribute to it through their taxes.
Goff welcomed the project, saying it will address congestion, transport emissions and the need for more housing in a high-quality, compact form.
Without light rail, he said, the growing city will become gridlocked and unliveable.
Robertson called the project the "most important infrastructure project that New Zealand has ever undertaken".
"It is crucial we get it right," he said.
Wood said it was the beginning of a "London-style" connected network that includes light rail to Kumeū and Huapai and a new harbour crossing.
Among the 18 or so stations would be a stop at the city's universities, Kingsland, Onehunga and Māngere, and a "support package" for affected businesses will be created, he said.
"We are making a commitment to businesses in the area that significant disruption will be addressed through a comprehensive package, including direct financial support."
Wood is optimistic about the ambitious timeframe to do the planning and consenting in three years and build the 24km route, including 11km of tunnelling, in six to eight years.
Auckland's 3.4km City Rail Link is a smaller project that is taking nine years to build.
Wood said the planning process is well underway with a lot of work already done, special legislation and fast-track consenting is likely, and technical experts had advised him the build would take six to eight years.
"Those are the estimates and we have confidence we can meet that," he said.
National's infrastructure spokesman Simon Bridges said the Government's light rail dream is just that – a dream, saying Prime Minister Jacinda Ardern promised in 2017 to build light rail to Mt Roskill in four years and all we have is an "option".
Light rail will be scrapped by National, the party's transport spokesman Simeon Brown told the Herald this week.
In an interview, he said the indicative business case is full of holes, it only just scrapes across the business case ratio of 1 and relies on tens of thousands of homes being built without taking into account the cost of the infrastructure.
"The number one priority for Aucklanders is a second Harbour Crossing for both public transport and private vehicles," Brown said.
Act transport spokesman Simon Court said New Zealanders from the Waikato to Southland will be on the hook for paying for Auckland light rail.
The Green Party said today's decision is the first step towards building the climate friendly, accessible city our communities deserve.
Transport Spokesman Ricardo Menéndez March said the Green's preferred option is for street-level light rail and by partially going underground the Government will need to ensure underground stations are accessible and welcoming to all communities.
The Government got a big tick from Infrastructure New Zealand for its "transformational Auckland transport plan" of pressing ahead with light rail and a second harbour crossing.
"This is New Zealand's biggest ever infrastructure project, and a comprehensive and integrated plan addressing long-standing issues and will make Auckland fit for the future and a great place to live, work and play," said chief executive Claire Edmondson.
The Dominion Rd Business Association welcomed the selection of tunnelled light rail, with manager Gary Homes saying it gives certainty to business and property owners after multiple false starts and dashed hopes for mass transit.
Māngere-Ōtāhuhu Local Board chairwoman Lydia Sosene was rapt with the decision to take light rail through Māngere, saying it will allow the transport poor community to get about the city on rapid transit and create job opportunities.