By 2018 almost all portions of the Manhattan Waterfront will have a permanent greenway path. There are, however, some portions of the island where challenges facing greenway implementation make only very long-term planning possible. These sites are expected to eventually have greenways, but when is not clear.

FDR
From East 51st Street to East 60th Street the FDR is at grade and directly next to the East River. To create a bike path in this area it is necessary to build a cantilevered structure outboard of the FDR. There are currently no plans for this to take place, but it would be possible in the event of future FDR reconstruction. Map and rendering of site.

Polo Grounds
From West 155th to West 162nd Street, the topography of the land and the proximity of the Harlem River Drive to the Harlem River demand that any waterfront bike and pedestrian path be a cantilevered structure. It is possible that this will take place as part of some future reconstruction of the Harlem River Drive, but there are no plans for this at present. Map and rendering of site.