The Evolving -- And Possibly Permanent -- Face Of Graffiti

"Of all the images from the 1970's and 1980's of a city out of control, perhaps none is etched more deeply into the public consciousness than that of the graffiti-covered subway train screeching into a station, every inch of its surface covered with a rich patina of spray-painted slashes and scrawls.

It took decades of work and millions of dollars to clean up the trains. But now officials are seeing a fresh surge of subway graffiti, in which windows are irreparably damaged with acid. Raising the specter of the bad old days, transit officials are vowing to fight a problem they say is even more menacing than the graffiti of decades past."