BMT West End Line

Elevated line over 86th Street at Bay Parkway station

Route designation on BMT Triplex equipment

The West End Line has had an express (on the BMT Fourth Avenue Line) service – labeled 3 in 1924 – since it opened in 1916, passing over the Manhattan Bridge and onto the BMT Broadway Line express tracks. In the late 1950s, midday trains were switched to the local Fourth Avenue tracks and through the Montague Street Tunnel, and late night and Sunday service became a shuttle between Coney Island and 36th Street. The express and local services were assigned the designations T and TT in the early 1960s. With the opening of the Chrystie Street Connection in late 1967, the B train from Manhattan was extended to Coney Island, absorbing the T and TT (both ran express on Fourth Avenue). The TT late night and Sunday shuttle survived until 1968, when the B became full-time. It ran local on Fourth Avenue during late night hours, but express at all other times. Late night operation was cut back to a shuttle to 36th Street in 1976.

In 2001, when reconstruction of the Manhattan Bridge north tracks resumed, the B service in Brooklyn was replaced by the new W train, which ran as a shuttle not only to 36th Street during nighttime hours, but also to Atlantic Avenue–Pacific Street on weekends. In 2002, reconstruction of Coney Island–Stillwell Avenue resulted in the West End Line being the only line to serve the terminal and the W was extended full-time into Manhattan, using the local Fourth Avenue tracks and Montague Street Tunnel on weekends and late nights hours.[8]

In 2004, the Manhattan Bridge reconstruction project was completed, and the W was replaced with an extended D train, running over the bridge at all hours and express on Fourth Avenue except late nights. D service was moved to the West End Line instead of returning to the Brighton Line, where it ran on from 1967 to 2001, because West End Line residents from Chinatowns in Brooklyn wanted full-time access to Grand Street, on the Sixth Avenue Line in Manhattan's Chinatown. This also eliminated the need to run late-night and/or weekend shuttles on either the Concourse Line or the West End Line.[9]

The other service pattern was the "West End Short Line", a rush-hour local (on Fourth Avenue) service between the BMT Nassau Street Line in Lower Manhattan and 62nd Street or Bay Parkway. It became part of the TT in the early 1960s and was discontinued in 1967. In 1987, the short line service was essentially recreated when the rush-hour M extension to Brooklyn was moved from the BMT Brighton Line to the West End Line terminating at Bay Parkway. It terminated at Ninth Avenue during midday hours until 1995, when it was cut back to Chambers Street. It was extended again from 2001–2004 while the Manhattan Bridge was closed for reconstruction. In 2010, as part of a series of MTA budget cuts, rush-hour M service was discontinued.

On July 19, 2019, a project to install elevators at the 62nd Street/New Utrecht Avenue station was completed.[10] Starting on September 18, 2021, and continuing until January 3, 2022, southbound D trains terminated at Bay 50th Street so work could be completed to protect Coney Island Yard from flooding.[11]