The 42nd Street Shuttle is a New York City Subway shuttle train service that operates in Manhattan. Part of a former Interborough Rapid Transit Company (IRT) line, it is sometimes referred to as the Grand Central/Times Square Shuttle, since these are the only two stations served by the shuttle. It runs at all times except late nights, connecting Times Square to Grand Central under 42nd Street. It is the shortest regular service in the system, running about 2,700 feet (820 m) in under two minutes.
The 42nd Street Shuttle is part of the A Division of New York City Transit, and the tracks that it uses opened in 1904 as part of the first subway in the city. In order to distinguish it from the other shuttles in the system, NYCT Rapid Transit Operations internally refers to it as the 0 (zero). Its route bullet is colored dark slate gray on route signs, station signs, and rolling stock with the letter “S” on the official subway map.