List of New York City Subway inter-division connections

The New York City Subway was formed from three different systems, the IRT, BMT and IND. For operational purposes, the IRT is "A Division" and the BMT and IND make "B Division"; however, common usage calls the three systems divisions. Over the years, various connections have been built to allow trains of one division to operate on the lines of another. For transfers, see List of New York City Subway inter-division transfers.

Revenue connections

Because the IRT system uses narrower tunnels and cars than the BMT and IND, the only possible inter-division revenue connections are between BMT and IND lines. The following connections have been built:
*October 30, 1954: IND Culver Line (originally called the Smith St. Subway) extended over BMT Culver Line
*December 1, 1955: BMT 60th Street Tunnel Connection between the IND Queens Boulevard Line and the 60th Street Tunnel
*April 29, 1956: IND Fulton Street Line joined to BMT Liberty Avenue Elevated (part of the Fulton Street Elevated, but disconnected from the BMT system and so is only used for IND service
*November 26, 1967: Chrystie Street Connection between the IND Sixth Avenue Line and the BMT Nassau Street Line (over the Williamsburg Bridge) and BMT Fourth Avenue Line (via the Manhattan Bridge) — Williamsburg Bridge connection no longer used for revenue service
*October 29, 1989: connecting tracks between IND 63rd Street Line and BMT 63rd Street Line (not generally used for revenue service unless a re-route of the NYCS service|R service is required north of 57th Street on the Broadway line).

Non-revenue connections

These connections mainly take place in yards:
*Crossover tracks (with third-rails) between northbound IRT Flushing Line and BMT Astoria Line at Queensboro Plaza (the Flushing Line's only connection to the rest of the system, originates from when both lines north of Queensboro Plaza were dual-operated).
*IRT Eastern Parkway Line and BMT Canarsie Line both have tracks into the Linden Shops. In addition, a single, non-electrified (no third rail) track connects these lines between Junius Street (on the IRT line) and Livonia Avenue (on the BMT line), in the Queens-bound direction only.
*IRT Broadway–Seventh Avenue Line and IND Eighth Avenue Line both have tracks to 207th Street Yard
*IRT Jerome Avenue Line and IND Concourse Line both have tracks to Concourse Yard
*Since October 30, 1954, the IND Culver Line has gone into Coney Island–Stillwell Avenue, where it connects to the BMT Brighton Line, BMT Sea Beach Line and BMT West End Line. For a short time in the late 1960s the NYCS service|NX service passed through Coney Island–Stillwell Avenue from the Sea Beach Line to the Brighton Line, but no service has passed through from the Culver Line.