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 New York City Subway nomenclature, a "line" refers to the physical trackage used by trains that are used by numbered or lettered "services"; the services that run on certain lines change periodically. Today, the division or company names are not used publicly, while the line names may occasionally be used.

Nomenclature

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 begins with a division (IRT, BMT or IND), which is its pre-unification division when applicable. 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 service operates along the IND Queens Boulevard Line as well as the BMT Broadway Line and the BMT Fourth Avenue Line. Each service is assigned a color. Since 1979, each service's color corresponds to the line it primarily uses in Midtown Manhattan—defined as the trunk line. There are three exceptions: the IND Crosstown Line, which does not carry services to Manhattan, is colored ; the BMT Nassau Street Line, which runs only through Lower Manhattan, is colored ; and all shuttles are colored. The list of trunk lines and colors is shown in the table below.

Line listing

There are currently rail lines. The Archer Avenue Lines and the 63rd Street Lines are each classified as two separate lines due to their structure: both lines have a distinct sections that are chained as BMT and the IND lines. In the list below, lines with colors next to them indicate trunk lines, which determine the colors that are used for services' route bullets and diamonds, as well as shuttle service lines. The opening date refers to the opening of the first section of track for the line. In the "division" column, the current division is followed by the original division in parentheses.

Inter-division connections

The following list shows the connections between the different divisions of the New York City Subway.

Purpose-built

These connections can be used by trains in revenue service: This connection is not for revenue service due to the differing widths of the trains:

Yards

These connections are located within the subway's rail yards and are not intended for revenue service.

Other

Unused connections in the same division

In some places, there are track connections within the same division that are unused in regular service.

Brooklyn

Manhattan

Queens

Unused center tracks

Many of the New York City Subway's lines have express tracks, unused in revenue service and generally only used for re-routes.

The Bronx

Brooklyn

Manhattan

Queens

Above ground sections

A majority of the New York City Subway is underground, but the following segments are located above ground level.

The Bronx

Brooklyn

Manhattan

Queens

Trackage

At minimum, in normal revenue service, all lines have two tracks, with one exception: the BMT Franklin Avenue Line has a single track between Franklin Avenue and Park Place.

Three-tracked portions

The New York City Subway has fewer triple track sections than it has quadruple track sections. These sections are listed below. The third track, when in use, is generally for peak-direction express service or reroutes, with exceptions noted below. Additionally, there are several pocket tracks in the subway where the line temporarily widens from two to three tracks, such as east of Eighth Avenue on the BMT Canarsie Line, and south of Court Square on the IND Crosstown Line.

Four-tracked portions

Quadruple-tracked portions of track are fairly common in the subway system. This makes it unique among most metro systems in the world, as most others only have two tracks per line. Generally, these portions are a pair of express and a pair of local tracks unless otherwise noted. The Bronx has no four-tracked lines. Pocket tracks are not included.

Defunct lines

The following New York City Subway lines are either entirely defunct or have major portions no longer in service. Defunct spur lines with one station, such as the South Ferry loops, are not included in this list, nor are surface transit lines.

Vestiges of former lines