Glenn Harlan Reynolds

It's yet another lesson in the law of unintended consequences — and, as usual, the government wants us to pick up the tab for its poor planning. This time, it's the Obama administration's proposal to allow tolls on interstate highways, where such tolls have been banned since the Eisenhower days.

The problem is that government efforts to discourage driving and to encourage fuel conservation have been successful. With people burning less gas, revenues from the gasoline tax are down.

People burning less gas is what the government wanted. But with gas prices at historically high levels (often over four bucks a gallon), and with trust in government at historic lows, politicians aren't too enthusiastic about taking the obvious step, increasing the gas tax. They don't want to take the heat. Instead, they're looking to increase revenue in other, less obvious ways.

This has led states such as Oregon and New Jersey to propose taxing people for mileage instead of gas, probably using GPS trackers. That approach increases taxes most on gas-sipping hybrids and electric cars, which use no gas at all. (You know, the cars the government has been busy subsidizing because they use less or no gas.) But the idea of having all our movement tracked by government-mandated GPS units hasn't played very well with voters, so those schemes have had trouble getting traction.

Tolls are plan B. But they'll also make the driving experience worse, and less private. If states set up old-fashioned toll booths on the interstate, as a number already have for bridges and tunnels, you'll have to slow down to pay. (Which, ironically, will waste gas.) Politicians will undoubtedly like it, though, because all those toll booth employees will be government employees who can probably be counted on to re-elect incumbents.

Of course, this is the 21st century, so we'll let drivers who opt in use radio frequency chips or bar codes to whiz by sensors that withdraw money from your bank account. But that's not really an improvement because it also means that the government will have a handy computerized record of where you go and when. It might not save time, either, as E-ZPass lanes clog up, too.

One of the nice things about driving in America today is that if you tire of the Big Brother aspects of air travel, you can just get in your car and go. Sensor-equipped tolls will make it easy for a government that already spies on us too much to spy on us some more. Whatever promises are made now, experience shows that's exactly what the government will do.

If the gas tax really isn't raising enough money to fix the roads, then our politicians should man up and increase it or better yet stop spending so much of it on sidewalks, bike lanes and mass transit. The worst possible outcome is tolls that instead of just taking our money like a gas tax, will take our money, waste our time and destroy our privacy.

Glenn Harlan Reynolds, a University of Tennessee law professor, is the author ofThe New School: How the Information Age Will Save American Education from Itself.

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