We've passed thru this tunnel several times--
Cumberland Gap Tunnel
The Cumberland Gap Tunnel is a 4-lane twin-bore mountain tunnel that is 4,600 feet long, and it carries US-25E under Cumberland Gap between Tennessee and Kentucky, and it was completed in October 1996 at a cost of $280 million.
The tunnel project was administered by the Federal Highway Administration's Eastern Federal Lands Highway Division, for the National Park Service.
IF a "dangerous cargo" truck wants to pass thru (ie- gasoline tanker,
propane tanker etc) They stop traffic and a guide truck with flashing lights
leads the truck thru. Once they exit the other end traffic is allowed to
resume.
They have a pull off on each end for us RV types to shut off our LP tanks
before we go thru.
Cumberland Gap National Park is a great hiking destination, especially
in the fall.