Many Auckland motorists will feel sceptical that road tolls are once again being touted as a possible answer to the city's growing transport problems. The reservations come on several fronts.

It has taken Wellington-based politicians years to come round to the idea, so any action remains several years away while an extra 800 cars clog up Auckland's streets every week.

There are several practical problems to work through before drivers can have confidence that tolling - euphemistically known as "congestion pricing" - will be fair and effective.

And there is the understandable Nimby effect. Just as many people say they support intensification to make housing more affordable ("but not in my street"), congestion pricing can sound reasonable until the cost forces motorists to leave their warm cars at home and stand at a rainy, windswept bus stop on a cold winter night.

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These are the challenges facing Government and Auckland Council officials who will work together on the Smarter Pricing Transport Project, announced by Transport Minister Simon Bridges and mayor Phil Goff this week.

The project will investigate whether or not to charge motorists to use certain roads - most likely motorways and main arterial routes - at busy times of the day.

Officials will test different options and evaluate whether they would improve traffic flows and how they would affect the city's households and businesses.

The idea is not new. In 2013 a team of business leaders and sector groups created by former mayor Len Brown concluded that either road pricing or fuel taxes were inevitable if Auckland was to solve its transport problems without unacceptably large rate increases.

A later report suggested $2 motorway tolls to raise an estimated $12 billion for more roads and better public transport.

At the time the Government flatly ruled out both ideas, prompting the council to levy a special transport rate instead.

The Government has eventually come round to taking road pricing seriously but is right to remain cautious about whether it will work.

Bridges has already acknowledged that any tolls must reduce traffic and road taxes from other sources should be handed back.

Anything short of this outcome will be seen as another revenue grab. Doubts also remain about the economic effectiveness of road pricing.

Will the cost of collection outweigh any benefits or can improved technology overcome this hurdle?

For road pricing to succeed, large numbers of people must decide it is too expensive for them to drive in rush hour, which could be seen as a tax on doing business or an imposition on many households' daily routine.

For instance, one of the most obvious contributors to Auckland's congestion is the crosstown school run, judging from the absence of traffic before 9am and after 3pm during school holidays.

But any attempt to push families into a different home-school-work travel pattern will raise other questions, particularly over Auckland's inadequate and overpriced public transport system.

Uber-style ride-sharing is an intriguing alternative but still in the very early stages.

If planners want to brandish the road pricing stick at Aucklanders, they will need to come up with plenty of carrots first.