A book entitled "LA's Lethal Air", produced by the Strategy Center in 1991, tells the fascinating back-story to L.A.'s current transit struggles. It sketches the history of transit in LA and describes how automobiles and under-regulated industry have made the air in the L.A. basin a poisonous soup.
  The most intriguing episode involves the formation in the 1930s of a new company, National City Lines, a partnership between General Motors, Standard Oil of California, Firestone Tires, Mack Manufacturing and B.F. Philips Petroleum. National City Lines' aim was to buy up the electric trolley system that had knit together the real estate developers' paradise of Southern California at the beginning of the century. Once that was accomplished, the company shut down these rail lines so that gasoline-powered busses and private cars would dominate the transportation market.
  This process began in 1936 and was completed in 1947. When it was all over, the car was undisputed king of Los Angeles, and across the nation, electric powered rail systems were on their way out as gas powered vehicles consolidated their hold on the people-moving business.
 

The desperately poor must rely on an aging and deteriorating bus system that lost 1000 buses between 1984 and 1996

  In his book "The Geography of Nowhere", social critic James Howard Kunstler recalls that GM was indicted for criminal conspiracy for its part in destroying the rail lines, "but the eventual fine of $5,000 was equal to the company's net profit on the sale of five Chevrolets".
  In Los Angeles, the legacy of the National City scheme is lived by millions every day. Anyone in LA who can come up with the money to do so, travels by car. The desperately poor must rely on an aging and deteriorating bus system that lost 1000 buses between 1984 and 1996. Cars choke the freeways and foul the air, while the neglected bus arm of the transit system means that even people who can afford no more than a $500 beater will venture onto the freeways rather than wait for a bus.
  However, thanks to the efforts of the Bus Rider's Union, this situation no longer appears inevitable, and even poor Angelinos can look forward to going back to the future.

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California Trolley and Railroad Corporation: www.ctrc.org