KEY POINTS:
Roads are not free. But Aucklanders won't pay tolls for new roads. Which has given the Government a Green headache.
The Government's alternative to tolls is a blunt, old-fashioned regional fuel tax, to pay for Auckland's passenger rail and new roads, and in Wellington for the Transmission Gully inland road north.
But the Greens won't vote for the tax unless it is blocked from being used for Transmission Gully and earmarked instead for public transport - which Gully champion Peter Dunne says has funding in the existing budget.
The Greens say roads are a privilege, not a right. Privilege has a price.
This view is not unique to the Greens. You could have tax cuts if staggering sums of tax revenue were not going on new roads, and if private companies built and ran some of them. But that would require tolls.
The most effective way to charge for roads is by Global Positioning System (GPS) tolling, charging every journey by tracking vehicles from satellites in the sky, varying the charges according to the road, time of day and congestion. Everyone could have a minimum allowance and pay for travel units above that.
Some European cities now have a form of GPS tolling. Here, some Ministry of Transport officials have argued the case informally for years. Get ready, it will come.
But paying for roads is not the Greens' point. Their interest in pricing roads centres on the externalities: pollution and greenhouse gas emissions, and the cost in human health and life of fumes and collisions. Road users should pay for those externalities, they say.
Tobacco taxes are based on the cost of fixing up the smokers, active and passive, and some of the fuel tax used to go to the health budget, but not since the Cabinet realised in 2005 that roads were an election issue and directed it all to transport infrastructure.
Expect to hear more of externalities. The Greens are no longer the outlier party they used to be, thanks to the climate-change frenzy, and co-leader Jeanette Fitzsimons' calm and grace.
The Greens are also no longer an outlier in the parliamentary mathematics, as the tussle over fuel tax shows.
Fitzsimons is the Government's spokesperson for energy efficiency and Sue Bradford is spokesperson for "buy New Zealand". In return the Greens abstain on the Budget and confidence motions, guaranteeing the Government's tenure - though last week's 61-vote for the Budget shows the Government does not yet depend on their abstention.
But wait. There's more.
If National falls short of a majority next election, and if New Zealand First falls out, and even adding Dunne and Rodney Hide still doesn't get National a majority, to which parties does John Key turn? The Maori party and/or the Greens.
Doing a deal with either for support or even just for abstention on crucial votes would be no doddle.
But Key is a conciliator and Bill English has been driving home to the party's regional conferences that they will have to learn - as Labour has - that their government may have to implement policies they dislike as part of deals with people they dislike.
With the Maori party, for example, a price of support might be rediscovering property rights as a core National principle and applying that principle to the foreshore and seabed.
The risk for the Maori Party and the Greens in such deals is that their core supporters will jib.
New Zealand First's Maori support fell when it went with National in 1996. Many of the Greens' core activists and supporters deserted when it joined the Alliance in 1992.
Nevertheless, there is a significant strand of thinking within the Green party that an abstention, or even support, deal could be done, if there was serious action on a swag of designated policies - more serious action and on a wider front than so far extracted from Labour.
Given National's flip on climate change, that cannot be ruled out. Labour, which counts the Greens as in its sphere of influence, might yet rue having cheese-pared its concessions to the Greens over the past seven years.
Can the Greens do that deal? This weekend at their conference they will as usual strive mightily to make all their decisions by consensus.
If the strand of thinking that contemplates a deal with National is to climb from "significant" to "serious", that will be a fraught decision for next year's conference and the wider membership. A discussion paper is being prepared.
The Greens have been in national politics now for 35 years. If they are to step up to serious influence, as climate change's new respectability invites them to do, they have at some point to risk getting real political mud on their hands.
