I find that Riverside narrows in the low 140's until you get past Riverbank Park, leaving very little clearance between parked cars and traffic. If you are coming from downtown the easiest way to get up to the bridge is probably to take St. Nicholas Ave., which cuts diagonally from Central Park North and meets Broadway at 168th street, then ride on 168th over to Ft. Washington and up to 178th from there. St. Nicholas also avoids the huge trough at 125th and at 155, is a gradual incline from 138th-157th, and has marked bicycle lanes. The surface is ok for the most part except around 163rd. If you start north on CPW, it runs into St. Nick at 121st.
As for the greenway, it is pretty quick, but you still have to get from the river up to the bridge.
Last edited by Trueblood; 06-21-09 at 05:43 AM.