The tunnel has two levels. The two tracks on the upper level, connecting the IND Queens Boulevard Line in Queens to the IND Sixth Avenue Line in Manhattan via the IND 63rd Street Line, are used by the . There are also track connections to and from the BMT 63rd Street Line, west of the Lexington Avenue–63rd Street station. The tunnel west of 21st Street/Queensbridge was placed into service in 1989, The final section of the 63rd Street Tunnel, connecting the 21st Street station to the Queens Boulevard Line, officially opened on December 17, 2001.