Transport Minister Steven Joyce should button his lip if the Auckland Council resolves to finance an inner-city rail tunnel from sources other than taxation. Road tolls and congestion charges are perfectly proper local devices. Having given the city a single voice, national politicians should listen to it.
Mr Joyce is not alone in remaining sceptical of the cost-benefit merits of the $2.4 billion underground rail loop compared with other transport needs. But his responsibility is to national taxpayers. If the Auckland Council can convince its voting residents to pay the full cost of the project without calling on central funds, sceptics will have to reassess their view.
A charge is the best test of real demand. A recent Herald-DigiPoll survey tested Aucklanders' enthusiasm for the inner-city rail loop against a Northern Motorway extension, Mr Joyce's priority. More than half, 63.3 per cent, preferred the loop. If that enthusiasm survives when they face the financial obligation, they must be confident the railway would be well patronised and roads less congested.
Mayor Len Brown has yet to convince the council, let alone citizens, that the inner-city loop is worth financing in this way, but it is too early to be dismissing the idea as the minister did last week.
"I don't think anyone would buy the suggestion that that very expensive project should just be paid for by road users," he said. Aucklanders, most of them motorists, might not buy that idea either, but it should be up to them. Mr Joyce need concern himself only with the interests of road users outside the city who should be exempted from Auckland Council charges unless they come into the city.
That could be done very easily by putting electronic toll readers on motorway off-ramps, thereby ensuring that traffic not destined for Auckland could pass through on the motorways for free. But any traffic leaving the motorways to use the city's roads and other amenities would pay the charge, and should.
New Zealand has long had a highly centralised system of government in which local government has been restricted to roles, powers and rate finance approved by Parliament. The creation of a single council for Auckland, which comprises a quarter of the country's population and more than a quarter of its wealth, poses a challenge to the national apparatus.
Central government has done much for Auckland's development but its decisions have not always been far-sighted. The Harbour Bridge is the shining model of an Auckland initiative, long delayed and frustrated by the reluctance of governments to provide finance or to allow the city to raise loans for its construction.
There was no reluctance then to pay for the project with a toll. When eventually the bridge was built, its use was so heavy that the capacity quickly had to be doubled and all capital costs were recovered long before tolls were removed.
The bridge and the motorways that came soon afterwards changed the shape of Auckland. They encouraged it to sprawl north, south, west and southeast, taking advantage of its harbours and coast but also depriving the city of coherent governance, which the new setup has been designed to provide.
Planners of the inner-city rail loop hope it will change the shape of Auckland again, stopping sprawl and concentrating population growth around public transport routes into a revitalised core.
Next they have to convince Aucklanders to pay for it. Road charging is a punitive way to pay for a railway but city road users might recognise it to be in their interest. It is brave of the mayor to propose it. He will need all his powers of persuasion. But having taken this step he can reasonably tell Mr Joyce to butt out.