The Allegheny River and Justus Trails can be accessed from several trailheads:

Franklin Trailhead - at the east end of the 8th Street Bridge over the Allegheny River on PA Route 322. There is easy bike access to downtown Franklin. GPS N 41 23.200 W 79 49.050
There is a second lot 1 - 1/2 miles east on Route, 322, at the base of Victory Heights Hill. GPS N 41 22.400 W 79 48.067