He is public transportation’s loudest cheerleader, boasting that he takes the subway “virtually every day.” He has told residents who complain about overcrowded trains to “get real” and he constantly encourages New Yorkers to follow his environmentally friendly example. But Mayor Michael R. Bloomberg’s commute is not your average straphanger’s ride. On mornings that he takes the subway from home, Mr. Bloomberg is picked up at his Upper East Side town house by a pair of king-size Chevrolet Suburbans. The mayor is driven 22 blocks to the subway station at 59th Street and Lexington Avenue, where he can board an...