 Under Mayor William O 'Dwyer and General Charles P. Gross , another plan was put forth in 1947 by Colonel Sidney H. Bingham , a city planner and former Interborough Rapid Transit Company ( IRT ) engineer . O 'Dwyer and Gross believed that construction of a Second Avenue subway line would be vital to both increasing capacity on existing lines and allowing new branch lines to be built . This plan would again connect the Second Avenue Line to Brooklyn . As with Pheifer 's proposal , a train frequency map was created ; however , Bingham 's proposal involved more branch lines and track connections . A connection to Brooklyn was to be made via the Manhattan and Williamsburg Bridge , and would allow trains from these bridges to go onto the Sixth Avenue Line or the Second Avenue Line . Other connections to the Second Avenue Line were to be provided at 57th Street , via a line connecting to the Sixth Avenue Line ; two express tracks would be built along that line north of West Fourth Street . The IRT Pelham Line would be switched to the combined IND / BMT division ( this plan also includes other connections , which have been built ) , and connected to the Second Avenue Line . The Second Avenue Line would end just north of that connection , at 149th Street , with transfers to the IRT White Plains Road Line and the elevated IRT Third Avenue Line , the latter of which would be demolished south of 149th Street . There would also be a connection to the IND Concourse Line . The line was to be built in sections . The Manhattan section was top @-@ priority , but the Brooklyn section was 19th on the priority list , and the Bronx section did not have a specific priority . 
