Chrystie Street Connection

The Chrystie Street Connection is a set of New York City Subway tunnels running the length of Chrystie Street on the Lower East Side of Manhattan. It is one of the few track connections between lines of the former Brooklyn–Manhattan Transit Corporation (BMT) and Independent Subway System (IND) divisions, which together constitute the system's B Division. A major branch of the IND Sixth Avenue Line, it connects the Sixth Avenue Line to the BMT Brighton Line and BMT Fourth Avenue Line via the north side of the Manhattan Bridge and to the BMT Jamaica Line over the Williamsburg Bridge. The project, opened in 1967 and 1968, also includes the Sixth Avenue Line's Grand Street and 57th Street stations, the latter of which is not part of the connection itself.

The connection was originally conceived as part of the long delayed Second Avenue Subway, and, along with the three stations added with the opening of phase 1, is one of the few completed sections of the project.

The two tracks that run the full length of the connection begin as a continuation of the IND Sixth Avenue Line express tracks east of Broadway–Lafayette Street. These tracks include the line's only station, Grand Street, and connections to the two northern tracks over the Manhattan Bridge. The IND Sixth Avenue Line express tracks formerly continued east, ending slightly east of the Second Avenue station, and were planned to extend into Brooklyn and beyond as part of a never-built major system expansion called the IND Second System. Those tracks still exist at Second Avenue station, but now connect to the local tracks west of the station.

The two tracks on the north side of the Manhattan Bridge formerly carried trains to the BMT Broadway Line, which now connects to the tracks on the south side of the bridge. The south side tracks had been connected to the BMT Nassau Street Line, carrying the Nassau Street Loop service via Chambers Street from 1915. The northern tracks of the bridge saw heavier traffic loads because it led to Midtown Manhattan, compared to the southern tracks, which made three stops in Lower Manhattan before returning to Brooklyn. As a result of the uneven traffic distribution, the Manhattan Bridge started tilting to its north side. The connection to the Nassau Street Line was cut north of Chambers Street before the Manhattan Bridge and is used for storage from the Nassau Street side.

The opening of the Chrystie Street Connection to the Manhattan Bridge allowed the integration of four major routes of the combined system. The BB service of the IND was through-routed with the T BMT West End Line service as the B, and the D service of the IND was through-routed with the Q BMT Brighton Line service as the D. In 2004, the Brooklyn routes and terminals of the B and D trains were swapped as part of the Manhattan Bridge reconstruction from 1986 to 2004.

The two tracks that connect to the Williamsburg Bridge split from the Sixth Avenue Line local tracks east of Broadway – Lafayette Street and feed into the BMT Nassau Street Line west of Essex Street. The purpose of this portion of the connector was to allow trains originating in northern and eastern Brooklyn and southern and eastern Queens to operate into Midtown Manhattan via the Sixth Avenue Line, rather than having to turn south along Nassau Street. The KK (later renamed the K) service, which used these tracks, proved unpopular; as such, it only operated from July 1, 1968, to August 29, 1976, when it was cut as part of an ongoing retrenchment of service during New York City's fiscal crisis.

The connection was used for a time to move equipment to and from the BMT Eastern Division, but was not used in regular service again until budget cuts forced a reroute of the M along the connection starting on June 27, 2010. The M had been rerouted to replace the discontinued V route on the IND Sixth Avenue Line and the IND Queens Boulevard Line to Forest Hills–71st Avenue.

A plan similar to the Chrystie Street Connection was proposed as part of the Second Avenue Subway (SAS) under the Board of Transportation's 1944–1948 Capital Program, with connections from the 2nd Avenue line to the BMT Nassau Street Line, the Williamsburg and Manhattan Bridges, as well as a new station at Grand and Chrystie Streets. This plan would have allowed service from Grand Street to run south to Chambers and Broad Streets on the BMT Nassau Street Line, providing an additional East River crossing via the Montague Street Tunnel.