In the wake of the deadly bomb blasts in London July 7, 2005, several U.S. cities stepped up security around their mass transit systems. The Bush administration raised the terror alert a notch to code orange for the nation's mass transit systems. The heightened alert applies to "regional and inter-city passenger rail, subways and metropolitan bus systems," said Homeland Security Secretary Michael Chertoff. << Click on the map at left to see some of them. Credits: CBS News, The Associated Press