How the Government plans to pay for Auckland's multibillion-dollar light rail

After years of light rail promises which have been light on delivery, the Government has finally committed to an option for Auckland.

They're going with a mixture of overground on the route from the airport, then tunnelling underground from Mt Roskill to the CBD.

It's projected to cost almost $15 billion and it's not just taxpayers who are going to pay for it.

"Cabinet has met and now endorses tunnelled light rail from the city centre to Māngere corridor," Transport Minister Michael Wood announced on Friday. 

Auckland Mayor Phil Goff described it as "the biggest thing that has ever happened to Auckland". 

The pitch is public transport, London-style. Starting at the airport, the tram will run overground next to State Highway 25 through Māngere, Onehunga and onto Mt Roskill.

It'll then pop underground and carry onto Kingsland, past the universities and - for now - finish at Wynyard Quarter, but will eventually go over to the North Shore.

The 24km route will have up to 18 stations and run every five minutes - just turn up and go.

"A quarter of Auckland's growth can be accommodated along this corridor," said Wood. 

The plan is - eventually - to have a fully connected network with trams, trains, buses and ferries linking the city from the north, south, east and west.

It all sounds very expensive. At this stage it'll be about $15 billion.

"The question 'how do we pay for it' is I'm sure one of the first questions I'll hear," said Finance Minister Grant Robertson. 

The Finance Minister wasn't wrong.

"There's a range of options," he responded. 

Taxpayers will pay for the lion's share and Robertson wants to borrow to build.

"If central government is serious about this kind of nation and city-building project then we do have to have a slightly different conversation in New Zealand about public debt," Robertson said. 

ACT leader David Seymour isn't sure it's worth it. 

"If the only way this project stacks up is for the taxpayer to borrow and prop it up then maybe the project doesn't actually stack up."

But it's not just the public purse bankrolling the project. If this project means your property price goes up, you'll likely also pay - possibly a tax.

"I don't think anyone would think it's fair with such significant public investment going into this project that some people might swoop in and make windfall gains," Wood said. 

It was met with mixed feelings in Mt Eden.

"I don't think that makes a lot of sense," one person told Newshub, while another asked: "There's got to be much easier ways to spend, what is it? $14 billion?"

The North Shore might be left a bit cross about their new crossing - another year of consulting before a decision on what, where and when will come next year.

The Transport Minister promises he's not back-tracking.

"Quite the contrary, we are bringing forward the timelines," he said. 

National MP Simeon Brown says it couldn't come soon enough. 

"The priority has to be a second harbour crossing - that has to be what gets delivered here in Auckland."

Aucklanders have heard the light rail promise before. In fact, 7.1 metres of press release pledges.

But the minister is promising it's for real this time, with shovels in the ground on early works next year.

"Construction estimates six to eight years so an end time for the project by approximately 2030 to 2031."

So it's 10 more years, Auckland, and that's only if light rail stays on track.