Public backing for a central Auckland rail tunnel is more than twice as strong as for the Government's proposed new "road of national significance" north from Puhoi.

Although a Herald-DigiPoll survey has found support for the tunnel strongest in Auckland, the $2.4 billion project is also enthusing other New Zealanders, who are taking an even dimmer view of the highway proposal than the city's residents.

The 3.5km tunnel proposal between Britomart and Mt Eden won support from 63.3 per cent of Aucklanders, compared with the highway, which was backed by 24.8 per cent.

Although tunnel support weakened to 48.1 per cent among non-Aucklanders, only 19.2 per cent said they believed the highway should get higher priority. That compared with 27.5 per who did not know and just 5.2 per cent who did not back either project.

Only 5.6 per cent of Aucklanders polled had no opinion, and 6.3 per cent did not think either project should go ahead, taking a slightly less charitable view than their fellow New Zealanders.

The pollsters asked 750 people, including 270 Aucklanders, which of the two projects they thought should be the greater priority for the region.

That meant a margin of error of 3.6 per cent for the overall survey findings, including 53.6 per cent total support for the tunnel and 21.2 per cent for the highway.

There was a 6 per cent margin for the results among Aucklanders, given the smaller number of those surveyed.

The Government wants to build the northern highway in two stages, starting in 2014 for an 18km section between Puhoi and Warkworth and in 2016 for a remaining 20km to Wellsford.

Although the full project is estimated to cost $1.65 billion, those surveyed were asked only about the extension to Warkworth ($980 million).

Auckland Mayor Len Brown said from France, where he is combining a holiday with his wife with inspections of public transport systems, that he was not surprised by the findings.

"Aucklanders know that the inner-city rail link will help unclog our roads, deliver economic transformation and means our region will be easier to move around by effectively doubling the capacity of rail lines to the west, east and south," he said.

Council transport chairman Mike Lee said the poll revealed a "sea change" in public support for rail transport over roads.

"It seems the public are way ahead of the National Government on this issue, not just in Auckland but across New Zealand," he said.

"And it seems to me that the Minister of Transport [Steven Joyce] in particular is still taking a very conservative roads-first, urban-sprawl approach which is out of step with the views of the average New Zealander."

But Mr Joyce said there could be no valid comparison between the two projects and the results were "not a massive surprise.
Those surveyed will no doubt be looking for a solution for the city's traffic problems," he said.

"No one is pretending that Puhoi-Wellsford is a solution for Auckland's traffic problems - it's a link between Auckland and Northland."

He said there was no single silver bullet for Auckland transport, and the Government was overseeing a huge range of work both through motorway developments and rail upgrades, including electrification.

"The CBD rail loop is potentially one part of the puzzle, but all the evidence says it's a reasonably small part with a big price tag."

The council's business advisory panel chairman, Cameron Brewer, whose group wants the rail tunnel built within six years, said the project was gaining considerable support but it was critical to identify new funding sources.