There was some confusion when the trail encountered Berryville Road and then vanished. We eventually figured it out after a lot of scrambling. The track (SenecaCreekGreenway3.geojson) has been cleaned up.
Equally surprising was the discovery that the Greenway trail criss-crosses with the Highland trail at Black Rock Road/ Mill. This has interesting implications for the Stone Mill 50M, which may alternate between the two trails.