The federal gas tax levy is so painfully low, even libertarian groups like the Reason Foundation are okay with hiking the tax. At least, that's the impression a reader could be forgiven for drawing from the Associated Press's January 2 story, "Motorists' habits spur call for tax increases":

WASHINGTON (AP) — Motorists are driving less and buying less gasoline, which means fuel taxes aren't raising enough money to keep pace with the cost of road, bridge and transit programs.

That has the federal commission that oversees financing for transportation talking about increasing the federal fuel tax.

[...]

"I'm not excited about a gas tax increase, but the reality is our current gas tax doesn't pay for upkeep of the system we have now," said Adrian Moore, vice president of the Reason Foundation, a libertarian think tank in Los Angeles, and a member of the highway revenue commission. "We can either let the roads go to hell or we can pay more."

But in November, Reason's Director of Transportation Studies, Robert Poole, found fault not so much with the revenue drawn in by the federal gas tax but in how politicians spend gas taxes on purposes other than building and repairing highways (emphasis mine):

One of the wisest principles of 20th-century highway policy was user-pays. When the gasoline tax was invented early last century, it was seen as a substitute for 19th-century tolling—a substitute that was easier to collect and hence more user-friendly. Groups that wanted the benefits of paved highways sold the public on the idea that the gas tax was not really a tax. Because the proceeds would be legally dedicated to developing and maintaining good roads, it was really a user fee.

In the 21st century, we are at the dawn of a long-term transition to cashless tolling, which will start with limited-access highways and may eventually encompass all roads. For a number of decades more, however, fuel taxes will remain the largest highway funding source. Consequently, we all have a stake in making sure highway user-tax revenues are spent wisely during these decades of transition.

Unfortunately, the last several decades have seen continuous whittling away at the user-pays principle. First, in the 1960s and '70s, came the creation of a mass transit account in the federal Highway Trust Fund, diverting user taxes to non-users. At the state level, constitutional protections for highway funds remain in force in many states, and most states still use fuel taxes mostly for highways—but devote a lot of other tax revenue generated from motorists (vehicle registration fees, California's sales tax on gasoline, etc.) to non-highway transportation.

At the federal level the erosion has continued each time Congress reauthorizes the federal program. Anti-highway groups keep coming up with catchy new rationales for diverting more highway user money away from those users: "fix-it-first" (i.e., don't add capacity until every last bit of maintenance backlog is eliminated), "safe routes to school" (more sidewalks and bike paths "for the children"), and more recently "complete streets" (every road must have bike paths and sidewalks). The latest, just out from Rails to Trails, is that the 2009 reauthorization must divert at least $9 billion for "active transportation," the kinds that make you huff and puff.

—Ken Shepherd is Managing Editor of NewsBusters