The Texas Transportation Institute estimates that highway congestion cost Americans $78 billion in 2007. The average person probably couldn't cite a specific number, but he knows it's a lot.
Quantifying the deadweight loss from congestion is one thing. Figuring out how to fix it is another. Proposed solutions fall into two categories: "build more capacity" and "do something else." Depending on whom you ask, the "something else" means congestion pricing, adding light or commuter rail, or encouraging more walking, biking, carpooling and flextime.
The "more capacity" crowd relies on common sense: if we add more lanes -- more capacity -- to a congested road, then the road won't be as crowded. The "do something else" crowd argues that increasing the capacity of a congested road simply induces more congestion as the new capacity attracts users from transit, alternate routes, and off-peak travel times. And the new residential developments that spring up along new roads inevitably pump even more cars into the system.
This debate cannot be won or lost with ideological arguments. It must be settled empirically. Economists Clifford Winston and Ashley Langer have entered the fray to do just that. Their empirical analysis shows that, although highway spending does tend to reduce congestion, it does so very inefficiently:
We estimate econometric models of the determinants of congestion costs to motorists, trucking operations, and firms and find that, on average, one dollar of highway spending in a given year reduces the congestion costs to road users only eleven cents in that year.
They also found that if highway spending were targeted most efficiently -- i.e., to those states whose urbanized areas experience the greatest travel delays and to those stretches of road where spending is most effective at reducing congestion -- annual congestion costs would fall as much as 40 percent.
But even so, the congestion cost savings from one dollar of highway spending in a given year would amount to a modest twenty-five cents in that year, indicating that such spending, even if allocated more efficiently, is simply not a cost-effective way to reduce congestion. We conclude that the evidence strengthens the economic case for congestion pricing of roadways and provides some insight into policymakers’ preference for public spending over road pricing to mitigate congestion costs.
Interestingly, they also found that cities do not benefit equally from investments in new capacity. Cities that begin with a heavy investment in capital stock -- i.e., a highly-developed road network with lots of alternate routes -- might see a reduction in congestion without inducing offsetting demand. (Networks of any kind provide increasing returns as they grow denser.) But . . .
we find that an increase in urban freeway capital spending in states (e.g., Maryland) that have merely above average investments in their capital stock increase a city’s congestion costs. In these states, the road network is sufficiently developed to serve a high volume of traffic. But when improvements to certain stretches of an urban freeway induce demand, the additional traffic may create congestion on other roads that may already be near congested conditions. Because these states have not invested in their road system to the highest extent, few alternative routings are likely to exist to diffuse the induced demand over an extensive road network. Thus, even if delays are reduced on part of an urban freeway that is improved, delays and congestion costs are likely to grow on unimproved roadways, resulting in a net increase in a city’s congestion costs.
That point deserves super-duper emphasis: Spending money on highways to reduce congestion, paradoxically, increases congestion without a dense network of roads to diffuse the induced demand. Adding capacity makes things worse. Any solution therefore must come from the "something else" category, whether it be congestion pricing, transit, or more walking and bicycling.
It ought to be clear that Austin is one of the "low investment" cities. Austin has a primitive highway network for a city its size. It's got I35, MoPac, the two northern cross highways, 290 and 183, and 290/71 along the southern mid-section. The city has few practical alternate routes for getting from Point A to Point B. Hence, an attempt to increase capacity on one of these roads will inevitably increase congestion on another road.
For example, TxDOT is pushing ahead with plans to increase the capacity of 290 from Manor west to 183 by making it a limited access toll road. But the increased traffic flow on 290 will push thousands of more cars onto congested 183, where, once there, they really have no option. What's worse, the "improvement" will feed thousands more cars into already hypercongested I35. It's quite likely that the extra congestion on the much busier I35 and 183 will swamp any time savings on 290.
Given the primitive state of our highway system, we Austinites really don't have much choice. Without a system like congestion pricing to manage demand, we're just pissing away our highway dollars.
