American Gridlock
Traffic is making millions sick and tired. The bad news? It's going to get worse unless things change in a real big way
What to do then? In the past decade, highway construction in major American cities outpaced population growth, and still congestion worsened--and worsened most precisely where the most new roads and highways were built. According to a study issued earlier this month by the Surface Transportation Policy Project, residents of the 23 American metro areas that added the most new road capacity per person in the 1990s saw the annual number of hours spent stuck in traffic increase by 70.4 percent. Meanwhile residents of the 23 metro areas that added the least new road capacity per person experienced a mere 61.9 percent increase in congestion. Why do cities that build lots of highways wind up with more congestion than those that do not? Economists call it "induced demand." Build a new road, and sprawling new development will soon spring up to take advantage of the land that becomes accessible.
These trends cause many to believe that nothing can or will be done to alleviate congestion. But doing nothing is not an option, either. Traffic is a phenomenon subject to what engineers call "nonlinear effects." Joseph Sussman, a civil and environmental engineer at the Massachusetts Institute of Technology, notes that if you plot how the addition of new vehicles onto a highway affects their average speed, you get a graph that looks much like a hockey stick. You can put more cars and trucks on a highway without much loss of velocity--up to a point. But as the highway approaches its carrying capacity, suddenly the addition of a single car will cause the speed of all of them to drop. At that point, the effect is completely out of proportion to its proximate cause. So when the proverbial traveling salesman decides to make that one last call at the end of the day, he can throw an entire metro area into gridlock.
The same principle applies to traffic patterns over the long term. Say your commute time has been increasing by about 5 percent a year for the past five years. It's annoying, but you're resigned to it. But then one year, the roads you travel finally reach their capacity. Suddenly, your commute time jumps by 25 percent. The year after that, it's an additional 60 percent. Now, leaving earlier for work doesn't help; taking back roads and assaulting speed bumps doesn't help; even having real-time traffic updates streaming into your car's newfangled telematic device still leaves you stuck in traffic for more hours a day than you have. So?
So, embrace change. A recent survey sponsored by Smart Growth America, a new coalition of public-interest groups, asked a cross section of Americans: "Which of the following proposals is the best long-term solution to reducing traffic in your state? Build new roads; improve public transportation, such as adding trains, buses and light rail; or develop communities where people do not have to drive long distances to work or shop." Three quarters of respondents called for either improving mass transit or developing less auto-dependent communities; just 21 percent called for building new roads. Talk about a tipping point. America's long love affair with the car, it seems, may have finally soured into a less healthy relationship, one based not on freedom but on its opposite.
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