Beginning today, all cars entering the 8-square-mile area of central London must pay an $8 toll. The action was taken by London Mayor Ken Livingstone to ease congestion in the city, where traffic moves at an average of less than 10 mph during the day. Officials hope the toll will cut the volume of traffic in the zone by 20% and raise $208 million a year for public transportation investment. Opponents of the congestion charging plan say it will put more pressure on London's overcrowded buses and subway when people choose public transportation over their vehicles. They also predict gridlock on roads surrounding the areas where tolls would be issued. A network of 800 cameras linked to a bank of computers polices the zone, photographing license plates between 7 a.m. and 6:30 p.m. on weekdays. Computers automatically check plate numbers against a national database. Entry points are marked with a white letter C in a red circle painted on signs and the road so that drivers will not miss paying the toll. The fine for skipping the toll is $65. Residents of the zone get a 90% discount. Exempt vehicles include taxis, emergency services and vehicles powered by alternative fuels.