Gas Tax: Out of Gas

Everyone wants to use less gasoline — to save money, to reduce greenhouse gas emissions, or to lessen our dependence on oil. So technological improvements in fuel efficiency are in general a good thing.

But there's a wrinkle: Our system for paying for transportation infrastructure depends heavily on per-gallon fuel taxes, so more-efficient vehicles tend to reduce the amount we pay per mile. But the cost of providing a mile of road doesn't go down at the same time. Moreover, fuel-efficient and electric cars require just as much road building and maintenance as any other car does.

Think of it this way: Most years I drive about 15,000 miles, and in 2020 I expect I'll drive about the same miles. But in 2020 my car will probably get twice as many miles per gallon as my car in 2000 did. That means I will be using half the gas, and paying half the gas tax, for driving the same number of miles.