Transport Minister says many questions remain over $2 billion-plus project.
Auckland Mayor Len Brown is putting on a brave face after receiving a lukewarm Government review of a glowing business case for his pet transport project - the $2 billion-plus central city rail tunnel.
Although Transport Minister Steven Joyce initially indicated scepticism about a claim in the business case that the tunnel would pay for itself three and a half times over by turning Auckland into an internationally competitive city, Mr Brown is calling the review "another important step" towards getting it dug.
Mr Joyce said yesterday in announcing the review by officials of the Ministry of Transport, the Treasury and the Transport Agency that the business case was a first step, but left questions unanswered.
"It would be irresponsible for the Government to even consider being involved with a project of this size without being confident about having the full facts," he said.
"The findings of this review will help us determine if, how and when to progress with the CBD rail link project and will give both central and local government the certainty needed."
Among questions for which the minister said he wanted answers was how many extra passengers it would attract compared with those who would catch electric trains without the tunnel, and what impact it would have on car travel and congestion.
He also wanted to know how the project related to the growth and productivity of the CBD and greater Auckland, and whether it included full capital and operating costs.
Although the business case puts the tunnel's cost at $1.99 billion, Mr Joyce says $340 million for extra tracks and trains would push the capital bill to $2.3 billion.
Consultants who compiled the business case - as part of a $5 million investigation for KiwiRail and the former Auckland Regional Transport Authority - said in response to initial questions from the Ministry of Transport that the tunnel would boost annual rail patronage to 47.6 million passenger trips by 2041.
They estimated that without a tunnel to turn Britomart from a dead-end into a through station for trains from opposite directions, patronage growth would peak at 22.2 million passenger trips by 2026.
The consultants said that without the double-tracked 3.5km tunnel from the western end of Britomart to Mt Eden, and its three new underground stations, rail was unlikely to cope with travel demand fuelled by a fivefold population jump in the inner city by 2041 - to 102,000 residents - and a 94 per cent growth in employment to 122,000 jobs.
They predicted a tunnel would bring trains carrying 24,926 passengers into central Auckland in the morning travel peak by 2041, compared with 7283 without an inner city rail loop.
The review is expected to take three to four months.