Livingstone will stand or fall by gamble

The High Court has allowed Ken Livingstone to go ahead with the biggest risk of his political career. By rejecting Westminster council's appeal against congestion charging, the judge has ensured that the Mayor will have to fulfil his promise to make London the world's first major city to charge for using its streets.

Congestion charging has always had much to commend it in principle. Rationing scarce road-space (by charging for it) is certainly more sensible than making people queue for it (as we do now, by congestion). However, as we move closer to Day One of the congestion charge, doubt will pile upon doubt. Is this an idea that looks good in theory but turns out to be ruinous in practice?

First, the good bit. Road speeds in central London are now under 10mph slower than a century ago. Anyone who has sat in traffic jams attempting a journey by car, bus or taxi (all are delayed, congestion is a genuine leveller) knows how frustrating and expensive delays can be. The randomness of London traffic is particularly aggravating: one day a journey lasts 10 minutes, the next it takes half an hour. Congestion charging should thin out the vehicles (a cut of 15 per cent is predicted) so that people willing to pay £5 will be able to make predictable and quicker trips.

The downside of the charge comes in part from the difficulty of administering it and partly from possible public reaction. No city of the size and complexity of London has attempted anything like this. The need for complex computerbased administrative systems has doomed many public-sector projects. A minority of the public will attempt to evade or undermine the charge.

Steve Norris, Mr Livingstone's Tory opponent for mayor, has dubbed the congestion charge a "poll tax on wheels". Herein lies the Mayor's second problem: how will the public react to paying the charge, to additional congestion just outside the zone (the cause of today's court case) or to the extra pressure put on the city's wretched public transport system?

In A democracy, electoral response is crucial. If the public rebels against the Mayor, his political career could well be over. He will have to ensure that public transport (in reality, just the buses) improve so much that the overall reaction is favourable. If there is any suggestion the charge is unworkable or that drivers are significantly evading it, there would be no reason to prolong the capital's misery. It would have to be dropped.

Today's decision in the High Court has ensured that next February London will be the site of one of the world's great urban traffic experiments. Massive pressure will now bear down on Derek Turner, the Mayor's officer in charge, and on Capita, the private company employed to make the bureaucracy work. If they succeed, cities all over the world will follow London's lead.

If they fail, Mr Livingstone will almost certainly lose the 2004 mayoral election.

? Tony Travers is director of the Greater London Group at the London School of Economics.