Phil Walter/Getty ImagesFor city commuters, the slow crawl through peak hour traffic each day is an annoyance as unavoidable as blustery spring weather.Call it the cost of living in the big smoke. But Auckland is now on a path to join a small group of cities that have decided the cost is negotiable.Last week, Auckland Council’s transport committee signed off three options for public engagement in November.The price of the proposed congestion charge, ranging from NZ$2 to $7 per trip, is still unsettled. But what matters more is its shape, which has changed much from where the plans began.In its earliest days, the proposal was a time-of-use charge in the narrowest sense. It involved a rush-hour fee on motorways and a handful of congested corridors, with much of the technology needed to support it already in place.But council modelling highlighted a problem with charging individual roads: drivers could simply avoid them.That runs headlong into the “rat-run” effect. Drivers avoid the charged stretch, pour onto local streets and shift congestion into suburbs never built to handle it.Auckland Mayor Wayne Brown has advocated targeted motorway charges for years, specifically naming the Northwestern between Lincoln Rd and Te Atatū and the Southern between Penrose and Greenlane.Auckland Transport’s own assessment found problems with this approach, with one earlier option leaving some freight journeys slower than before. Traffic might flow more freely on the charged road, only for some of that congestion to be displaced onto surrounding streets.The three options now being considered take a different approach, focused on cordons around the city centre and, in the most extensive version, core motorways.The missing detailSingapore, London, Stockholm and now New York are held up as proof that road pricing works. All four drew a ring around the city centre, so entering from any direction means paying.More importantly, those cities also ensured there were other options for people heading into the CBD. London ran an extra 560 bus trips into the morning peak and carried 29,000 more passengers into the zone.Stockholm ran a seven-month trial, then held the referendum that made it permanent. Support went from 36% before it started to 52% while it ran, and past 70% by 2011.New York answered the money question before switching anything on. Revenue was committed 80% to the subway and buses and 10% each to the two commuter railways, and the transit agency borrowed US$15 billion against it. Drivers could see what they were buying.Auckland has proposed its own ring around the city centre. What isn’t yet clear is precisely how public transport would be expanded, improved or kept affordable for the people the charge is meant to move.When it opens later this month, the City Rail Link will put twice as many Aucklanders within a 30-minute train ride of the centre.But most people arriving in the city centre still come by bus, and those services are already busy. Albany’s park-and-ride has 1,210 spaces and fills by about 8am.Auckland Council has not said how many extra buses or feeder services would accompany each proposed option. Until it does, nobody knows whether the network can cope with a large mode shift.A charge, or just a toll?A congestion charge only works when people have meaningful alternatives to driving.A cleaner starting before dawn at Auckland Hospital doesn’t have a choice. Nor does the plumber whose van is their job. They can’t be waved towards a train and declared a problem solved.The Automobile Association said as much when laws to support time-of-use charging were introduced in 2024. Its policy director Martin Glynn noted the legislation exempts emergency vehicles and buses and nothing else, leaving out tradespeople who move in and out of the city all day.The plumber, at least, can come out ahead. The council’s modelling suggested business car trips would be faster under every option. Paying $5 for a trip that saves 12 minutes is a deal most tradespeople would take. But it is only a deal if the road actually clears, and the cleaner does not get one either way.That is the difference between a congestion charge and a toll. A charge is priced to change behaviour and needs somewhere for that behaviour to go. A toll simply collects, often taking most from the people least able to avoid it.Where does the money go?There are also unanswered questions about where the revenue would flow.According to the legislation, revenue must first cover the scheme’s costs and then go into land transport within the scheme region. Council officials have said this could fund public transport improvements.But it doesn’t say how the money would be divided between the NZ Transport Agency, Auckland Council and local boards. This would be settled later, in an investment agreement and an Order in Council nobody outside the process has yet seen.So, Aucklanders are to be asked what they think about congestion charging, without being told exactly what it will pay for or whether a single extra bus turns up before the first charge is levied. Arguably, these aren’t details that should be tidied away afterwards.As other cities have shown, circling a CBD with a congestion charge can unclog streets and cut traffic emissions. But Auckland Council appears to be heading into consultation without yet answering some of the questions that will determine how well its own scheme works.Timothy Welch does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.