By David Shepardson (Reuters) – New York City could introduce a traffic congestion charge of up to $23 a day late next year, which a study released on Wednesday projected would reduce the number of cars entering Manhattan by 15% to 20%. The city wants to charge a daily variable toll for vehicles entering or remaining within the central business district, defined as between 60th Street in midtown Manhattan and Battery Park on Manhattan’s southern tip. New York, which has the most congested U.S. traffic, would become the first major U.S. city to follow London, which began a similar charge in 200…