it is a regressive tax, so the 50 bucks more would impact the poor more than anyone else. It might work if the money went to infrastructure.
I believe that the increase in road use tax would be a better idea, since it is the big rigs and their weight that does the most damage to the infrastructure.
Of course, all politics is local, and in my case, it is 150 miles one way to the nearest full service town. So your assumptions on mileage per year and gas expense don't work for my particular situation, and probably don't for many rural people. In the sticks, we don't have a public transportation option, and a Prius won't work to get us over the pass for 5 months of the year.
I get where you are going but i wouldn't vote for that particular scenario.