The 47th–50th Streets–Rockefeller Center station (formerly 47th Street–50th Street–Rockefeller Center) is an express station on the IND Sixth Avenue Line of the New York City Subway. It is located along Sixth Avenue (Avenue of the Americas) between 47th and 50th Streets, on the west side of Rockefeller Center. The station is served by the D and F trains at all times, the B and M trains on weekdays, and the train during rush hours in the peak direction. , it was the 12th busiest subway station in the system. The Rockefeller Center station was built for the Independent Subway System (IND), which had first proposed constructing a line under Sixth Avenue in 1924. The line's construction was delayed by a decade due to negotiations with the Hudson & Manhattan Railroad. A contract for the line segment that includes the Rockefeller Center station was awarded in 1936. The station opened on December 15, 1940, and its mezzanine was expanded in the late 1950s and the early 1970s. The New York City Transit Authority proposed renovating the Rockefeller Center station in the 1990s, but the station still has not been renovated . The 47th–50th Streets–Rockefeller Center station contains two island platforms and four tracks. The northbound platform has the traditional arrangement of local service on the outside track and express service on the inside track, but the southbound platform reverses this (local on the inside, express on the outside). There is a full mezzanine above the station, connecting with Rockefeller Center. The station contains elevators, which make the station compliant with the Americans with Disabilities Act of 1990. The tracks diverge to the Eighth Avenue, 53rd Street, and 63rd Street lines to the north, and the southbound tracks cross over each other to the south. History Construction New York City mayor John Francis Hylan's original plans for the Independent Subway System (IND), proposed in 1922, included building over of new lines and taking over nearly of existing lines. The lines were designed to compete with the existing underground, surface, and elevated lines operated by the Interborough Rapid Transit Company (IRT) and Brooklyn–Manhattan Transit Corporation (BMT). The IND Sixth Avenue Line was designed to replace the elevated IRT Sixth Avenue Line. In 1924, the IND submitted its list of proposed subway routes to the New York City Board of Transportation (BOT), which approved the program. One of the routes was a segment of