Gas taxes go down when people use EVs. The government raises the yearly tax for EVs and hybrids, though not based on distance driven (where I am). I can imagine they do it in places with more EVs or where there are more controls like smog tests.

Or, why not put the road tax on tires, which wear based on distance driven? I suppose that might get kind of high if you're paying $0.005 per mile and the tires are supposed to last 50,000 miles for a total of $250 for 4 new tires.