How tall is your rig? I just completed a 3-week
trip to the NC/VA mountains, and spent some of the time up on the Parkway. At one of the visitor's centers I was asking about low clearances. The very helpful lady showed me a list of all the tunnels on the entire parkway. It listed their mile-post locations and the height of clearance (as well as a little more info that I didn't care about.) My rig requires 10' 6", and I found that one of the tunnels has only a 10' 6" clearance. I'd be a little hesitant about going through that tunnel. It's located at milepost 459.3, which is well south of where I was going to be.
I took pictures of the four pages of the book she showed me, and I've posted them
here as a public service. It shows 26 tunnels, three of which are below 13' clearance.
-Speak