Glenn Reynolds of Instapundit comes out against replacing the gas tax with a mileage-based levy, which would likely be assessed via a GPS-style "black box" installed in cars. The irony behind the reform idea? People are burning less gasoline, which is one of the goals of transportation policy. But that means government collects less money from the gax tax.

From Road & Track:

The response in many places -- from Oregon to New Jersey and points in between -- has been to propose taxing people based on the miles that they drive rather than on the gas that they burn.  There are even test programs going on in several states in which GPS trackers are being used to collect drivers’ mileage.  Needless to say, this sort of thing has people worried about privacy, especially in the wake of the recent scandals involving government spying and abuse of data.  It also raises the question of whether, by moving to a mileage tax, we’re giving up on trying to get people to save gas....

After noting that tracking drivers in this way creeps out privacy advocates, Reynolds further notes:

Simpler still, of course, would be an increase in the gas tax.  Politicians don’t like that, because tax increases are never popular, and gas is already expensive enough.  But, of course, the mileage tax would be a tax increase too, since the whole reason it’s being proposed is because the highway administrators want more money than they’re getting now.  If you’re going to pay more anyway, why give up your privacy to boot, just so that politicians can pretend something else is going on?  And the gas tax is still a pretty good proxy for road use:  The heavier the vehicle and the more it drives, the more gas it burns and the more tax its owner pays.  Hybrids get better mileage (though often no better than diesels) but that’s not enough to undermine this much, and pure-electric cars are a tiny fraction of those on the road, and that isn’t likely to change any time very soon.

Read the whole thing here.

The federal gas tax hasn't increased in about 20 years and, unlike most levies, is more clearly designed as a user fee - the money collected is supposed to be used for highway and infrastructure upkeep (though it's often diverted to other purposes). Note that Adrian Moore of Reason Foundation favors trying out the black boxes. He believes that privacy concerns can be addressed while getting more accurate tallies. From an LA Times story:

Wonks call it a mileage-based user fee. It is no surprise that the idea appeals to urban liberals, as the taxes could be rigged to change driving patterns in ways that could help reduce congestion and greenhouse gases, for example. California planners are looking to the system as they devise strategies to meet the goals laid out in the state's ambitious global warming laws. But Rep. Bill Shuster (R-Pa.), chairman of the House Transportation Committee, has said he, too, sees it as the most viable long-term alternative. The free marketeers at the Reason Foundation are also fond of having drivers pay per mile.

"This is not just a tax going into a black hole," said Adrian Moore, vice president of policy at Reason. "People are paying more directly into what they are getting."

More here.