The 4th tunnel heading toward North Carolina in Doe River Gorge is just past a dilapidated deck truss bridge over the Doe River. It’s crossable. Careful, though. The tunnel is centered at36.250708, -82.156534 and it’s filled with water. (read the comment on this)
There are two bridges over the Doe in the Gorge. One still has a truss superstructure, but precious little else and the other is as described above.