THE 拢5-per-day congestion charge for driving into central London, introduced in February 2003, cut emissions of some greenhouse gases by nearly 20 per cent in its first year.
From the number, speed and type of vehicle moving through checkpoints in London, Sean Beevers and David Carslaw of King鈥檚 College London calculated that nitrogen oxides and particulates fell by 16 per cent. A fall in the number of cars and an increase in speed of 4 kilometres an hour were responsible for three-quarters of this fall, with greener technology in cars making up the rest. Carbon dioxide emissions fell by 19 per cent. Even an increase in the number of buses, whose diesel engines are among the worst polluters, could not offset the drop, partly because modern buses are fitted with particulate traps.
Cities in the US, Japan and Europe have been following the scheme鈥檚 progress, but the next city to follow London鈥檚 example may be Edinburgh in Scotland, which will be holding a referendum on congestion charging early next year. 鈥淓dinburgh is unlikely to meet national air quality targets in 2010 without the introduction of congestion charging alongside a range of public transport improvements,鈥� says Donald Anderson from the City of Edinburgh Council.
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But congestion charges may not be enough to fight pollution, especially when the charge covers only a small part of a city 鈥� a mere 1.3 per cent in the case of London.
鈥淔ewer cars and faster speeds accounted for significant drops in nitrogen oxides, particulates and carbon dioxide鈥�
An unusually hot summer in 2003, which led to slow-moving air masses and easterly winds, brought extra pollution to London from Europe, making the city鈥檚 air pollution worse than it had been in the summer of 2002. 鈥淚f you had made a simple comparison you鈥檇 come to the conclusion that the effect of congestion charging was to make air pollution worse,鈥� says Beevers, whose work will be appear in Atmospheric Environment. 鈥淭hat鈥檚 clearly nonsense.鈥�
