Shortly after dawn on February 17th 2003, the world's most ambitious road pricing experiment will start in London. Though cordon toll schemes have been operating in Norway for years, and Singapore has an electronic system, no one has ever tried to charge motorists in a city of the size and complexity of London. For decades, transport planners have been demanding that motorists should pay directly for the use of roads. According to the professionals, it is the only way of civilizing cities and restraining the growth of inter urban traffic. Politicians have mostly turned a deaf ear, fearing that charging for something what was previously free was a quick route to electoral suicide. But London's initiative suggests that the point where road pricing becomes generally accepted as the most efficient way to restrain traffic is much nearer than most drivers realize. The mayor of London, Ken Livingstone, has pinned his political reputation on the scheme's success. If it works, cities around the world will rush to copy it. If it fails, he will be jeered from office when he seeks re-election in 2004. But how will success be judged? The mayor claims that congestion charging will produce ￡130m in net annual revenues, reduce traffic in central London by 15% and reduce traffic delays by about a quarter. Unfortunately these ambitious targets are unlikely to be met. For a start, the low level at which the charge has been set owes more to politics than traffic planning. Its impact, modest in comparison with the already high ￡4 an hour on-street parking charges in the area, may be less than anticipated. But most transport experts are cautiously optimistic that it will help improve the capital's chaotic transport system. As for the mayor, his political prospects look good. Those who drive cars in the center of London during the day are a tiny fraction of the millions who walk or use public transport to get to work. London's willingness to take the plunge has moved congestion charging from the realm of transport planners into mainstream politics. Yet the low-tech solution it has adopted has been overtaken by modern microwave radio systems allowing cars to communicate with roadside charging units. The next generation of technology will use global positioning satellites (GPS) to track the position of vehicles wherever they are, on a second-to- second basis. The brave new world of paying as you go is not far away. For those who drive in rural areas, the cost will come down. But for motorists who spend most of their time in congested urban areas, travel is rightly going to become much more expensive. We can learn from the first paragraph that in the world the scheme of tolling systems is