Originally Posted by twobikes
Noticed last week Big Witch Tunnel on the Blue Ridge Parkway. Eastbound,it's signed 11' 10" Westbound it's signed 13' 7" ???
Big Witch Tunnel, length 348 feet, maximum height 18'1", minimum height 11.3", elevation 4412 fet above sea level.
Chances are, the road is not exactly centered in the arched tunnel. The eastbound side is closer to the edge of the tunnel, on the outside of the curve, so the lowest point over the eastbound traffic lane is lower than the lowest point over the westbound lane which is on the inside of the tunnel's curve.