The first phase of the Second Avenue Subway opened in January 2017, from 63rd Street to 96th Street, and is served by the Q train.[1] The full Second Avenue Line will be built in four phases, and the planned T service will not run until the third phase of the line opens from Houston Street to 63rd Street.[2] Currently, the third phase is not funded or scheduled.[3]
From 1961 to 1968, the T and TT designations were also used for trains running along the BMT West End Line in Brooklyn, which was replaced by the B train and later by the W. The West End Line is now served by the D train.