In the New Republic this week, Clay Risen argued that the recently-passed highway bill was a stinking, steaming pile of rotten pork. Of course. Not only that, though, but it failed to address the most dire transportation-related problem facing the nation today—congestion:

According to a May 2005 study by the Texas Transportation Institute (an arm of Texas A&M), congestion alone costs the economy $65 billion a year. If national highway capacity continues to expand at its current, meager 3 percent annual rate, it's not hard to imagine the economic impact that the expected doubling of truck traffic over the next 15 years will have. Whatever that economic impact is, it will certainly swamp the benefits accrued from a few thousand more jobs.

What I'm not sure about, though, is how much Congress can really do about congestion. Building more roads or expanding highways doesn't tend to help, since the new capacity very quickly—sometimes almost instantaneously—becomes congested again, as more and more people decide to take advantage of the new roads. Now obviously new roads need to be built—and they work very well in fast- or newly-growing areas—but I can't imagine that any large region can afford to build enough to eliminate congestion.

Alternatively, the federal government could dish out more money for public transit projects, as it just did for Los Angeles County. But public transit by itself won't always reduce congestion. "Light rail" systems often shuttle suburban commuters to and from a district, but not around or within the suburbs, where much commuting takes place. Meanwhile, depending on how the system is designed, commuters often have to drive to the station anyway, which can put more cars on the road. Public transit works best, it seems, when it's accompanied by good land-use policies—building offices and residential areas near transit stops. But the power to do this doesn't lie with Congress, but rather with a district's ability to get its citizens to actually care about sprawl, as well as their ability to put developers in a headlock, which often depends on having a strong local economy.

At any rate, even in the optimal case, public transit would have a very small effect on congestion, simply because not that many people would use it outside large urban areas: Anthony Downs of Brookings estimates that even if public transit were "tripled and fully utilized," it would reduce morning private vehicle trips by 8 percent. Not bad, and worth doing, but not enough to make even a decent-sized dent in congestion—and maybe not even worth it on a cost-benefit analysis. The same criticism applies to building more high-density housing, again, see Downs. New Urbanism is cool and totally worthwhile, but don't expect it to make anymore than a modest dent in national congestion.

So that leaves us with peak-hour tolls or road-pricing schemes. Assuming that Americans would ever go for them, which seems unlikely right now, pricing schemes have worked beautifully in the downtown areas of London and Singapore (where alternative modes of transit are available), but not quite as well elsewhere (from what I've heard, correct me if I'm wrong). Sadly, though, most of America just isn't like the downtown areas of London and Singapore. Meanwhile, high-occupancy tolls—i.e., extra pay-to-travel lanes—don't actually seem to reduce congestion, though they do give folks who can afford it a way to circumvent traffic jams.

I'm probably being unduly pessimistic, but it seems that barring some nifty scientific advance—based on, say, the traffic-flow research described here—or a radical overhaul in the way the United States is arranged, we're probably just stuck with congestion as an unpleasant fact of life. How terrible this is depends on your perspective: Many places seem to suffer congestion, typically, as a side-effect of a strong economy. (Congestion rose sharply in the Bay Area during the internet boom, for instance, and then plunged after 2000.) So perhaps thinking of traffic jams as a "cost," or a policy failure, is the wrong way to go about it. I don't know. But if they are inevitable, then Congress really should worry more about creating the sort of jobs that make congestion worthwhile in the first place. And whoever's designing the flying cars, by the way, needs to work a bit faster.