The mayor of London told dozens of world mayors that they could unclog city streets and fight global warming by charging hefty fees for driving in congested areas of their communities. Mayor Ken Livingstone said making drivers pay a "congestion charge" to drive in central London has improved traffic flow and reduced the emission of "greenhouse gases" blamed for raising temperatures and changing weather patterns. The $9 fee has forced people out of their cars and filled city buses, subways and sidewalks, he told mayors assembled here Friday for the U.N. World Environment Day Conference. "We are the only city...