The Governor of Oregon has come under fire for wanting to replace the gas tax with a mileage tax. He wants to use GPS to track residents' mileage, and then assess the tax at the pump.
At first glance, this might seem like the right way to assess the tax. Wear and tear on roads is more closely related to miles driven than to gallons of gas consumed. In practice, it's a terrible mis-assessment of taxes, raising questions of jurisdiction, cost-to-revenue matching, government-sponsored behavior modification, and CAFE standards. And that's without the intrusiveness of the government watching where you drive your car.
If gas tax revenues are down, it results from some combination of better mileage and less driving. Better mileage undermines the argument for higher CAFE standards, as it happened without them.
Less driving - supposedly the behavior we all want - shows the dangers of using the government as a massive behavior-modification program. Governments do a terrible job of matching revenue structure to cost structure; if successful, the programs that were dependent on sinful excess suffer.
I've written about Denver Water's experience (and now neighboring Aurora's experience) a couple of times. Almost all of their costs are fixed, so higher charges result in lower usage, and less revenue, but does little to lower costs. They raise rates even further, enraging consumers who are already watching their yards turn brown in years of plentiful snowpack.
We've seen this with smoking. Smoking in the US is down, and yields on tobacco-backed revenue bonds are up. Long-term bonds paying 5% coupon are routinely priced at 9% yield-to-maturity. This in a declining interest-rate environment, with a tax-free coupon. Often, these bonds are now rated at just over junk level.
Ideally, fees would allocate taxes to the roads being driven and their maintenance costs, from the drivers using them. But it isn't necessary to tax each driver preicsely; it's only necessary to make sure that aggregate collections match aggregate costs.
A mileage tax would tax only Oregonians. But they drive in neighboring states, and Washingtonians and Californians use Oregon's roads. All things being equal, I'm most likely to fill up in a jurisdiction where I do most of my driving. And under such conditions, a point-of-sale system would ensure that every jurisdiction would collect its fair share of road use taxes over time.
All things being equal. Of course, they're not. I no longer drive out of my way to get better gas prices. But I will try to nurse a tank to get to the cheapest gas near my regular route. Bureaucrats argue that this leads to competition. As though there were something wrong with that.