The 42nd Street Shuttle is a line and service of the IRT division of the New York City Subway. It is sometimes referred to as the Grand Central/Times Square Shuttle, since these are the only stations served by the shuttle. It runs at all times but late nights, connecting Times Square to Grand Central Station under 42nd Street. Instead, for late nights the 3 is used. It is the shortest regular service in the system, running 0.8 mile (1.3 km) in officially one minute. In order to distingush it from the other shuttles in the system, NYCT Rapid Transit Operations refers to it as the "0".
The southbound express track on the four-track line was closed and new platforms were built, as the old station at Times Square had been local-only. However, the new arrangement turned out to be inadequate, and the shuttle was closed on midnight between August 3–4 for expansion of the platforms. The shuttle reopened on September 28, 1918, with improved passageways and platforms. On the walls of the stations, black bands (at Times Square) and green bands (at Grand Central) were painted to guide passengers to the shuttle platforms.
The shuttle ran at all times until September 10, 1995. Today, it runs at all times except late nights, when the 3 provides replacement service. When the shuttle is closed, the area is sometimes used for movie and TV filming. The French Connection and King of New York, among many other titles, were filmed on the 42nd Street shuttle.
Of the four shuttle tracks, only three are in use, the former southbound express track space being used for platform space at each terminal. The former southbound local track is now Shuttle Track 1; Track 2 no longer exists; the former northbound express track is Track 3; and the former northbound local track is Track 4.
Tracks 1 and 3 are connected to each other and to the Lexington Avenue Line's southbound local track south of Grand Central station. Track 4 connects to the Broadway-Seventh Avenue Line's northbound local track north of Times Square station. There is no connection between tracks 1 and 3 on the one hand, and track 4 on the other; therefore, although the shuttle was once part of the original through-route of the first IRT subway, it is now physically impossible for a train to go from the IRT Lexington Avenue Line through to the IRT Seventh Avenue Line or vice versa by using the shuttle tracks.
In service, each of the shuttle tracks in operation at any given time is independent of the other; e.g.., the train on track 1 simply runs back and forth on track 1, and there is no switching involved in reversing at each terminal. To provide for quick turnaround of the shuttle trains, there is an operator at each end of the train. Depending on which direction the train is traveling the operators swap jobs when the train gets to one end; one acts as the operator in the front and the other acts as conductor in back.
"Open New Subway Lines to Traffic; Called a Triumph," New York Times, August 2, 1918, page 1
"Drop Shuttle Plan as Subway Crush Becomes a Peril," New York Times, August 3, 1918, page 1
"Subway Shuttle Resumes Today," New York Times, September 28, 1918, page 17
"A Subway Station is Shuttered, the First in 33 Years," New York Times, September 11, 1995 [the article is about Dean Street on the Franklin Avenue Shuttle, and the headline refers to the 1962 closing of Worth Street; several old-style elevated railways were closed since then, as well as the Culver Shuttle which hosted both elevated and subway service at one time]