Most bridge clearance signs allow room for snow pack on the road. But, it's not guaranteed. So, I prefer to not take the gamble.
I have seen places with a swinging bar hung over the road with a sign on it that says "if you hit this sign, you will hit that bridge". And "Actual Clearance".
Semi-trucks don't go to gas stations they go to truck stops with pumps designed to handle big rigs and overhead canopies tall enough for the big trailers. If you have a truck that uses diesel fuel I suggest you use the truck pumps at the travel centers.
Flying J has RV pumps with both gas and diesel available. Plenty of clearance above, and on the sides.