If the gas tax were a fuel gauge, its needle would be quivering pretty close to Empty. As great as hybrid, electric, and fuel-efficient cars are for the environment, each new one to hit the road diminishes gas tax revenue. Even if states increased the tax — which many have refused to do for far too long — its long-term viability as a funding mechanism is doubtful at best.
The most compelling replacement for the gas tax is a vehicle-miles traveled fee. From a funding perspective, a V.M.T. fee would certainly level the playing field: instead of paying road taxes at the pump, drivers would pay based on how much they drive. But for some people, the idea of having the government track their every movement is just too creepy to accept.