Starting at the intersection of Library and Clifton Roads in Bethel Park where the Orange Belt currently terminates from the southwest, the former segment begins at PA 88 South through Library and Finleyville (Washington County), then continues left onto Washington Avenue / Finleyville–Elrama Road, left onto PA 837 North (back into Allegheny County), and right onto PA 51 South for 2 miles to the current southeastern terminus at PA 48 North.