List of New York City Subway inter-division connections

The New York City Subway is a heavy-rail public transit system serving four of the five boroughs of New York City. The present New York City Subway system inherited the systems of the Interborough Rapid Transit Company (IRT), Brooklyn-Manhattan Transit Corporation (BMT), and the Independent Subway System (IND). New York City has owned the IND since its inception; the BMT and IRT were taken over by the city in 1940. The former IRT system is now known as the A Division, while the B Division is the combined former BMT and IND systems.

In the nomenclature of the Subway, the terms "line" and "service" are not interchangeable with each other. While in popular usage the word "line" is often used synonymously with "service" (even sometimes on the website of the MTA), this list will use the formal usage of the term "line."

A line is the physical structure and tracks that trains run over. Each section of the system is assigned a unique line name that is paired with its original division (IRT, BMT or IND). For example, the line under Eighth Avenue is the IND Eighth Avenue Line. Some lines have changed names (and even divisions), but this happens relatively infrequently.

By contrast, a service refers to the route that a train takes across the various lines. A service can operate along several lines and even along different divisions. For example, the R service operates along the IND Queens Boulevard Line as well as the BMT Broadway Line and the BMT Fourth Avenue Line.

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