Refers to graffiti on or in subway cars as well as in subway stations. A tradition of subway graffiti originated in New York in the early 1970s and quickly spread to other large urban centers in the United States and the rest of the world, especially in Europe. Like other types of graffiti, aerosol spray paint and permanent markers are the most common media. Subway graffiti typically consists, in part, of an artist's name, nickname, or 'tag.' For graffiti in subways but considered art, combine indexing with "graffiti art."