IND 63rd Street Line
The 63rd Street Line is a rapid transit line of the New York City Subway system, running from connections with the Broadway-BMT Line at 57th Street and 7th Avenue and the 6th Avenue Line at 47th-50th Sreets Rockefeller Center station on Sixth Avenue on the western and the Queens Boulecard Line in Queens at the eastern end. There is also provision to connect to the Second Avenue Line from west to north and south to east when and if it is built.
The 63rd Street lines
The 63rd Street Line is actually two separate subway lines, a BMT line from 57th Street and 7th Avenue to an uptown connection with the future Second Avenue Subway, and an IND line from 47th-50th Streets and 6th Avenue to Queens. The two lines share only one point of contact, west of Lexington Avenue, where double crossovers allow northbound and southbound trains of either line to crossover to the other line. At Lexington Avenue, a double-decked station will allow acorss-the-platform transfers between the two lines, similar to the arrangement at Queensboro Plaza. Trains to Queens (and later Upper Manhattan) use the upper level and trains to downtown Manhattan the lower level. Currently the BMT tracks are behind a wall on the platforms on each level, which will be removed when the tracks are active.
The IND line is currently the only one to carry regular passenger service, hosting F service 24/7. The tracks are coded as new chaining route "T" (T1 and T2).
The BMT line is used for non-revenue moves. switching west of Lexington Avenue to access the Queens-bound tracks of the IND line. It is occasionally used for revenue service as a bypass, and hosted shuttle service to Long Island City for a while during construction. The tracks are coded as BMT chaining route "G", the same as the 60th Street tunnel and Astoria Line as tracks G3 and G4 to distinguish them from the pre-exisiting G1 and G2 tracks, The BMT tracks end at bumper blocks east of Lexington Avenue and are to be connected to the Second Avenue Line in the future.
The 63rd Street Tunnel is a two level tunnel, hosting the 63rd Street Line on its upper level. The lower level, currently without service, is to carry the Long Island Rail Road's new terminal line to Grand Central Terminal.