IThe Stern Report repeats what your man has been saying for a very long time, see Deep-fried Hillman Imp; Scotland's Transport: namely that Margaret Thatcher's "great car economy" has become in the less-than-long term untenable. Traffic pollution is the one greenhouse-gas generator which has stubbornly continued to rise, and Labour's near-deathbed turn to conservation measures must be contrasted with its supine acceptance of mobility-out-of-control while in office. Alistair "safe pair of hands" Darling accepted "predict and provide" as the only target for road and air traffic. But while commitment to Sir Nicholas Stern's remedies - curbs on road and air, improved public transport - may benefit the Greens, the Scottish National Party may have trouble in imposing green values on its heartlands, since it is in its north-eastern constituencies largely a rurally-based party and has voters disproportionately reliant on road transport. This could limit its appeal to green voters but need not do so.

It is true that such taxes as congestion charges are regressive, and will penalise car-dependent regions and voters. But a Scottish government might accommodate both by introducing carbon-trading on a regional basis as a means of funding power as well as transport. It should be possible to calculate, region by region, the miles run by particular types of vehicles and their cost, distinguishing between essential work/shopping/school/tourist trips and those which could be performed more fuel-efficiently by other forms of transport. The domination of Scottish retailing by supermarkets is a self-dug hole, but not without remedy. Even in rural areas there's some scope for "green" economies: in the Scottish Borders the General Hospital at Melrose, for example, has about 800 parking spaces, many of which are not just unnecessary but actively harmful to patients' health. The same (though without the toxic element) goes for the Borders Council at Newtown St Boswells. A pick-up and dial-a-bus fleet providing free to work and local journeys, and subsidised car-sharing, would leave a much smaller carbon footprint.

But the best pay-off may be the following. In many rural areas, not just in Scotland, necessarily higher car use could be to some extent offset by the export of renewable energy generated by wind, water, solar or biomass, along with energy saved by using local insulating materials, and pollutants that can be buried in "carbon-sequestration" schemes. Something akin to the present transnational carbon-trading, buying and selling permits, could provide a subsidy to fuel costs in rural areas, or aid the purchase or conversion of road vehicles using LPG or hybrid drives.

The Scottish central belt and its urban and semi-urban areas - housing perhaps 70% of the population - are in a different situation. European precedents, in Switzerland and Germany, indicate that these could drastically lower their carbon emission by investing directly in better and more demand-responsive public transport, walking and cycling. This can be done through a "trickle-down" system whereby trunk diesel and electric rail schemes liberate additional buses to build up new high-volume corridors; through "bespoke" strategies for big travel centres such as hospitals, schools, airports, etc.; and subsidies to win key groups to public transport, cycling, and walking. Or combinations of these: in Tübingen off-peak buses (which are all two-door) can carry 5-6 bikes on uphill trips. Road closures and traffic calming can make life a lot safer for walkers. In Tübingen the mile to my office has only one main road crossing. When I used to walk from Islington to the old British Library I took my life in my hands on six.

Should the SNP form a Scottish government, it will probably be in alliance with the Greens, so it must be prepared to prioritise projects. It is committed to the scaling-down of the Edinburgh Airport rail link, estimated to cost over £600 million: quite properly in view of Stern's doubts about the sustainability of air travel. But is the M74 extension to create a Glasgow urban motorway, which it backs (although already rejected by the Official Reporter), on the same level as the almost inevitable replacement or rebuilding of the Forth Road Bridge?

Likewise, improvements to the existing Anglo-Scottish rail routes should come before any new high-speed link to London. The Edinburgh-Glasgow railway ought to be high-speed, sure. Options can be kept open on a Maglev solution, if computerised improvements can bring the cash and environmental costs down. Pro-tem there should be a rebuilt Edinburgh-Glasgow via Shotts line, giving a half-hour trip, with a Carfin-Uddingston-Motherwell triangle linking it to the West Coast Main Line. But why not an incremental programme of improvements to both main lines: a model of Anglo-Scottish cooperation? Tunnels under the long drags to the summits at Beattock and Shap, high-speed stations at Carlisle and Newcastle, deviations avoiding sharp curves at say Berwick and Morpeth and a general programme of flyover junctions, extra tracks and level-crossing replacements? These are probably capable of bringing the Scotland-London trip down to three hours.

But the real priorities of a Scottish government must be improving and electrifying rail routes within Scotland itself, on which speeds are no better than in the days of steam. A high-speed Inverkeithing-Glenrothes line and the regrading and doubling throughout of the Dundee-Aberdeen railway would reduce times from the central belt to Dundee to 45 minutes and to Aberdeen to an hour and a half. Napier University's recent calculation that rail travellers are 66% more productive while underway than car drivers is self-evident (there seems a causal relationship between Scotland's less-than-effective business class and too much time spent at the wheel of the company car). Slow-running, poky diesels are no alternative. But electrified and rebuilt rail can probably hold its own against the car and even against domestic air travel, once security and check-in delays are added in.

Functions such as retail must also be restructured, after Stern's inevitably pessimistic assessment of the global costs of out-of-town, car-based shopping centres. Even here, there may be no need for drastic measures, as some supermarket chains are already adjusting to deliver rather than to attract car customers: something that opens up a new future for local shops and post-offices as pick-up points.

In an overall redistributive sense, this suggests regional energy authorities trading permits with each other. This could be a planned process or a market one, or the Holyrood government could experiment with both. It would both simulate local enterprise (fuel suppliers, buses and delivery vans, smaller shops and co-operatives) and create a benign cycle of energy-saving. If the SNP can find such solutions for its rural clients, it could do a deal with the Greens and attract support from a Labour party whose transport record has been abysmal.