I travel up I 81 pretty regular. As a matter of fact, I buy diesel fuel at a station at Exit 77, 100 miles from home because it is the least expensive fuel on my travels in either direction.
Gasoline is also less expensive.
Virginia could easily raise the fuel tax by from .07 to .10 per gallon and be in line with prices in adjacent Tennessee and still less than North Carolina.
Based on adjacent states, Virginia fuel is under taxed.
Or, looked at another way, perhaps fuel in adjacent states is overtaxed.