"The Los Angeles Air Pollution Control Board is established in 1946 in an effort to discover the cause of the brown cloud hanging over the city and decide how to combat and disperse it. In 1949, after intense lobbying from both the automobile and oil industries, and against the recommendations and position of the Los Angeles Air Pollution Control Board, the public rail system, which at one time was the largest in the world, and still serves a majority of the city's population, is decommissioned and torn out. It is replaced by a small fleet of buses."