Ruth Brandon: EU study shows how to clear up clogged cities

What cut congestion and pollution the most was a rise in car-operating costs

Three pieces of recent news should set us all thinking. First, Britain's CO2 emissions rose during 2003, despite Government plans to reduce them. Second, congestion charging has been so successful that Ken Livingstone is thinking of extending it. And third, since 1997, the real cost of motoring in the UK has fallen by 5 per cent, and will fall further this year.

Clearly, Government policy on transport and pollution is deeply contradictory. A piece of research just published by the EU might help. Propolis is a three-year project on how transport policies affect cities. The cities studied were Helsinki, Naples, Brussels, Dortmund, Bilbao, Vicenza and Inverness.

The aim of Propolis was "to find policies that could ... improve all dimensions of sustainability" compared with existing plans. The models show the results of different scenarios over 20 years.

Inverness, a small town in a thinly-populated area with few congestion problems, is perhaps the least typical. But its plans have a familiar ring. They include the restriction of development to urban and brownfield sites; rises in housing density; parking restrictions; more walking and cycling; improved bus services; and new rail links between Inverness and the coastal towns that constitute its hinterland.

Inverness's plan, typically, more or less runs to stand still, although by 2021, 13 per cent less fuel would be used, and pollution and greenhouse gas emissions would fall.

The Propolis team then imposed various scenarios on this basic model. Two involved public transport, one reducing travel times by 10 per cent, the other cutting fares by half. These had little effect.

With car-entry pricing, like London's congestion charge, people transferred to buses, walking and cycling; when the charge was raised, some jobs moved to outlying towns.

Raising parking charges produced a greater effect: employment in the city fell 11 per cent, and was redirected to small towns where parking was free. Population distribution outside Inverness rose by about 15 per cent, while within the city it fell slightly. But this dispersal increased the average length of car trips, and hence greenhouse gas emissions, by 20 per cent.

The scenario that really altered living patterns, however, was an increase in car-operating costs. When these were doubled, the percentage of journeys by car dropped 12 per cent, bus use rose 12 per cent, and walking and cycling increased by 120 per cent. Employment grew within Inverness itself. And as people moved nearer their work the population rose, by 18 per cent in the central urban zone and 13 per cent further out.

This scenario also cut the length of car journeys by 10 per cent, reduced greenhouse gas emissions by 37 per cent, and cut air pollution.

In the larger cities, a combination of public transport policies and car pricing produced the best results, especially where money from car traffic and extra fares was invested in public transport. But some policies have unexpected results: where public transport is made cheaper and more efficient, private car mileage may actually increase, as families move further from the city.

What the study shows is that population and employment patterns are bound up with transport in complex and sometimes counter-intuitive ways. Real improvements can be made; but piecemeal solutions of the kind we currently see not only make no sense: they may even achieve the opposite effect to that intended.

Ruth Brandon is the author of 'Automobile: How The Car Changed The World', published by Macmillan