Auckland Mayor Len Brown expects a $2 billion rail tunnel through central Auckland to be completed within seven years, but who will pick up the bill remains uncertain.
The tunnel, linking Britomart with Mt Eden station and creating an inner-city rail loop, was one of Brown's primary election campaigning points and the business case was released today.
A report on which the proposal is based says the standard benefit-cost ratio (BCR) for the project is equal or higher than that of two of the Government's Roads of National Significance.
Speaking at a press conference in Auckland today, Brown said he was determined to have trains running on the new route within seven years.
He did not specify how the project would be funded, but was confident of support from the Government and other "sources".
"We know that there is a significant cost there but I'm confident that we can, with all the various tools available to us, deliver it over the time frame that I've indicated."
Transport Minister Steven Joyce said it was highly unlikely the government would pay for the bulk of the project.
"It would be more like some form of partnership, once we've got over the hurdles and it all makes sense, then it would be about Auckland making a contribution and the Crown making a contribution," he said.
"Firstly we need to have a good close look at it, it's a huge amount of money."
Joyce said the total cost would be up to $2.7 billion.
"It's $2 billion if you don't talk about the additional trains to make it run, and additional infrastructure," he said.
"Either way, it's very expensive. There's been no commitment of money either from Auckland or from the government."
Brown said the tunnel was vital as it would turn Britomart from a dead-end station to a through station, thus making it possible to run many more trains in Auckland.
"The link would double the number of trains that can go through Britomart, let Aucklanders get around the region more easily, and reduce congestion on our roads. The report can't be ignored," Brown said.
"The potential urban redevelopment and additional growth derived from investment in this infrastructure would make the project transformational not just for Auckland, but for New Zealand as a whole."
The tunnel would include new stations near Aotea Square (which could become busier than Britomart), Karangahape Road and Newton.
Brown said the report suggests there is a strong case for proceeding immediately with protecting the route, funding the protection process and further investigation of funding the tunnel.
As much of the route would be underground, affected landowners would need to be consulted about potential impact to their properties.
The report suggests that without the link, the central business district would require twin or triple bus lanes in both directions on most road corridors, Brown said.
"The rail link is quite possibly the most critical element in Auckland's transformation into a globally competitive urban centre, and this report confirms that."
Joyce said the report talked about journey kilometres, but not about the number of vehicle trips into the city that would be saved.
"It's difficult to ascertain the actual effect of what is a very expensive project," he said.
"It's equivalent, on the roading side, to the Waterview Connection, plus an extra lane in each direction on the North-Western Motorway, plus the Victoria Park tunnel, plus the Manukau Harbour crossing, and at least half the Newmarket Viaduct."
Joyce said the report talked about congestion but didn't get into the detail of how that would be addressed in terms of actual numbers.
He took issue with the report's statement that the standard benefit-cost ratio (BCR) for the project was equal to or higher than that of two of the Government's Roads of National Significance.
"They have released a BCR with Webs (wider economic benefits) and they've been a bit naughty because they've called it a BCR," he said.
"Then they've gone out beyond the NZTA evaluation manual and said `by the way, we've got a new way of calculating it which improves it even more'.
"What they've tried to do is compare the BCRs, including Webs, on the tunnel project with the plain BCRs of the two other projects."
Joyce said the actual comparisons, at the level of BCRs including Webs, were identical.