BMT Jamaica Line

The BMT Jamaica Line, also known as the Broadway - Brooklyn Line, is an elevated rapid transit line of the B Division of the New York City Subway, in Brooklyn and Queens, New York City, United States. It runs from the Williamsburg Bridge southeast over Broadway to East New York, Brooklyn, and then east over Fulton Street and Jamaica Avenue to Jamaica, Queens. In western Jamaica, the line goes into a tunnel, becoming the lower level of the Archer Avenue lines in central Jamaica. The J and Z trains serve the entire length of the Jamaica Line, and the M serves the line west of Myrtle Avenue.

The longest elevated line in the system, the Jamaica Line includes the oldest existing elevated structure in the system – the original 1885 line of the Brooklyn Elevated Railroad, the former BMT Lexington Avenue Line between Gates Avenue and Van Siclen Avenue – as well as the newest elevated structure, the 1988 ramp into the Archer Avenue subway.

The Brooklyn–Manhattan Transit Corporation (BMT) originally operated the line with "westbound" trains heading toward Manhattan and "eastbound" trains heading toward Canarsie, Middle Village, or Jamaica, generally in agreement with compass direction. However, NYCT's railroad directions, which are north and south, replaced the BMT's west and east railroad directions, respectively. This reclassification resulted in services which ran through the BMT Nassau Street Line to Downtown Brooklyn having two south ends. To eliminate any confusion, the directions of train services in the eastern division were switched, with trains running towards Jamaica being considered Northbound. The KK (later K) and current M services were an exception to this, with Jamaica, Broadway Junction, or Metropolitan Avenue remaining the south terminal, since they used the Chrystie Street Connection from the Jamaica Line to the IND Sixth Avenue Line.