A few weeks ago, Ben Adler wrote a piece for The American Prospect about how both the White House and Congress are under-funding mass transit. Now I agree, more money for transit could cut down on automobile use and carbon emissions, and reduce urban sprawl. Worthy goals all around. But it's also worth wading a bit deeper in the weeds to see how perverse federal funding for transportation really is.

A Brookings Institution report on the subject from 2003 compared the funding process for highway and mass transit projects, and discovered some rather stark differences. The federal government will usually cover about 80-90 percent of the costs for a new highway project, and only about 50 percent of the costs for a transit system, under new rules. Local communities have to pick up most of the rest of the tab, with state governments chipping in some. Since that bill often requires new property taxes, people generally prefer to build highways. (Indeed, thirty states restrict their gas tax revenues to highway purposes only.)

And it gets worse. Under federal rules, transit projects have to undergo far more scrutiny. Before Congress hands out money for transit, they demand a cost-benefit analysis of the system, an analysis of its effects on land use, an environmental analysis, and often a comparison among various alternatives. Now, that all sounds perfectly reasonable, except that highway projects don't have to undergo most of these procedures—except for a looser environmental analysis. Federal oversight is rather minimal. Highway money is basically a gift to states and local communities.

Not surprisingly, many of those communities find it far easier to build new highways than to set up, say, a light-rail system, no matter how popular the latter may be. (The report gives an example of this happening in Milwaukee.) So yes, more money for mass transit. Fantastic. But it also looks like the funding rules need to be changed, so that transit and highway projects can compete on an even playing field.