Last month, Barack Obama traveled to snowy St. Paul, Minn., the same place where in the sunnier days of June 2008 he predicted that his clinching of the Democratic presidential nomination would be remembered as "the moment when the rise of the oceans began to slow and the earth began to heal."
This time in St. Paul he addressed a lesser problem, one within the ambit of a president's powers: transportation.
He mentioned the most common form of transportation -- auto travel over streets and highways -- only in passing. Instead, he hailed St. Paul's "spiffy new trains," one of which was derailed downtown two hours later.
But he did make one very practical and sound point. And that is that you have to find a way to pay for these things.
What he failed to mention is that the funding source for federal transportation spending is drying up, in part because of his own policies. That's the federal gas tax, enacted as part of the Interstate Highway program in 1956 and last raised in 1993.
Gas tax receipts are on a downward trajectory, for multiple reasons. One reason is that people have been driving less, and not just because of the recession. Average monthly driving, the Volpe National Transportation Systems Center reports, peaked at 900 miles in 2004 and was down to 820 in 2012.
Young people, glued to smartphones and video games, are less likely to drive or even get driver's licenses. Commuting is down, with employment still below pre-recession levels.
And the Obama administration raised gasoline mileage standards to 35.5 mpg in 2016 and 54.5 mpg by 2025 -- far above the 2013 average of 23 mpg. These sharp increases mean that less gas will be sold and much less revenue will be generated by the 18.4 cent per gallon federal gas tax.
In addition, the government is promoting hybrid and electric cars, whose owners pay less or no gas tax -- even though they cause wear and tear on highways. Owners of natural gas vehicles -- promoted on a bipartisan basis by Sens. Jim Inhofe and Carl Levin -- would pay no gasoline tax at all.
This has left congressional transportation committees in a quandary. Raising the gas tax is considered highly unpopular. Obama's solution in St. Paul -- "simplifying the tax code" -- doesn't seem to be in the cards any time soon.
All of which undermines the argument that the gas tax is a user tax, in which those who use roads tend to pay for them.
Fortunately, there is another and better kind of user tax available. That, as the Reason Foundation's Robert Poole has argued, is per-mile tolling.