1. check out traillink.com
from the west bronx, you can connect vis van cortland park.
from the east, bronx river path to e 233rd, up 233rd to centarl ave and stay on till tuckahoe road
west on tuckahoe to nepperham to saw mill river road which will take you towards the trailhead. there was once a sign on saw mill rd that pointed to the trailhead.
go to the westchester.gov and look up the maps for south and north county.
when you get to the end at elmsford there is a detour you must take ( look for warehouse road) to connect to the north county.
need further info write my private address. I rode to NYC from Springfield MA via the north & south county.
ed