The problem with the greenway up there is accessibility. You can get on it easily from 181st St, by going from the bridge up to Ft Washington Ave, left under the bridge, and then left again. You use the pedestrian walkway over the highway at the end of 181st. OR, you can take Riverside down to 95th St and go in from there. The only other way on is around 125th St, but I never go that way. It'll take you down to the Fairway. As far as I know, all other entrances require stairs.