My experience with all the tunnels in the area is, if your gas is on you pull off and turn it off and then continue. I have pulled off when the gas was turned off and they act like why did you stop??? If the gas is off apparently you don't have to pull off but I don't see any signs that tell you that. You will see many campers that don't stop.
You can go to the
http://www.virginiadot.org/travel/hr...ult.asp#hazmat and read the rules