At the CEOs for Cities blog they’re observing that last year the United States saw a dramatic decline in the volume of traffic congestion driven by a modest decline in total vehicle-miles traveled:
New data show that in 2008 the amount of traffic congestion in the nation’s cities declined by 30 percent, and that congestion was [...]
At the CEOs for Cities blog they’re observing that last year the United States saw a dramatic decline in the volume of traffic congestion driven by a modest decline in total vehicle-miles traveled:
New data show that in 2008 the amount of traffic congestion in the nation’s cities declined by 30 percent, and that congestion was lower in every hour of every day in 2008 than it had been the year previously. How did we make these big gains? Not by adding more highway lanes or transit—the physical infrastructure barely changed—we did it with a very modest decline in car travel. On urban interstate highways, total vehicle miles traveled in the US declined by about 3 percent in 2008.
Part of what’s notable about this is that the decline in congestion is gigantic relative to the decline in driving. This is because:
[T]raffic congestion is subject to a tipping point–what economists call non-linearities. Add an additional car to a crowded road at rush hour, and traffic slows down a bit, and then the “carrying capacity” of the road declines. Traffic engineers estimate that most roads carry their maximum throughput — number of vehicles per hour at about 40 miles per hour — so as traffic slows below that speed, the road actually loses capacity and goes slower and slower, producing a traffic jam.
Basically, what we saw last year was this same tipping point in reverse. To tackle America’s congestion problem by building new roads would be hideously expensive, not workable at all in many metro areas (where’s little-to-no space to add roads), and almost certainly futile over the long run. But what this natural experiment suggests is that to tackle congestion with “demand management” policies such as congestion pricing and market-rate parking would be relatively easy. In other words, you would only need to decrease the volume of peak-hour traffic by a pretty modest amount in order to produce a dramatic gain in the ease with which traffic flows. Meanwhile, the modest charge would generate some revenues that could be used for public purposes.
Advocacy of congestion pricing of roads has come to be associated with a more general movement for a reinvigoration of pedestrian- and transit-oriented lifestyles, but in many respects this is misplaced. I live in a walkable, transit-accessible neighborhood in a central city. I don’t own a car and get around on foot, on bike, on bus, or on Metro. Consequently, it doesn’t really bother me if other people have unnecessarily long commutes. Ultimately, neither drivers nor non-drivers benefit from bad policy that causes unnecessary traffic jams and inconvenience, but it’s regular car commuters who are paying the highest price.
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