SR 78 connects Appalachian with several coal mining communities in western Wise County.

The state highway heads east and immediately turns north onto the old alignment of Main Street, which parallels US 23 Business.

SR 78 crosses Callahan Creek and curves northwest onto Callahan Avenue to pass under US 23 Business, which crosses over the creek, the state highway, and a Norfolk Southern Railway spur line, formerly part of the Interstate Railroad, on a sweeping bridge.

The state highway intersects several auxiliary rail spurs on its way to the hamlet of Stonega.

SR 78 reaches its northern terminus at an arbitrary spot south of the clusters of houses that form Stonega.