3/1/11

Fewer Roads, Less Traffic

Not fewer drivers, but fewer roads. This is fascinating:
A case in point is “The Price of Anarchy in Transportation Networks,” published last September in Physical Review Letters by Michael Gastner, a computer scientist at the Santa Fe Institute, and his colleagues. Using hypothetical and real-world road networks, they explain that drivers seeking the shortest route to a given destination eventually reach what is known as the Nash equilibrium, in which no single driver can do any better by changing his or her strategy unilaterally. The problem is that the Nash equilibrium is less efficient than the equilibrium reached when drivers act unselfishly—that is, when they coordinate their movements to benefit the entire group.
The “price of anarchy” is a measure of the inefficiency caused by selfish drivers. Analyzing a commute from Harvard Square to Boston Common, the researchers found that the price can be high—selfish drivers typically waste 30 percent more time than they would under “socially optimal” conditions.
The solution hinges on Braess’s paradox, Gastner says. “Because selfish drivers optimize a wrong function, they can be led to a better solution if you remove some of the network links,” he explains. Why? In part because closing roads makes it more difficult for individual drivers to choose the best (and most selfish) route. In the Boston example, Gastner’s team found that six possible road closures, including parts of Charles and Main streets, would reduce the delay under the selfish-driving scenario. (The street closures would not slow drivers if they were behaving unselfishly.)
Science proves it- jerks are suboptimal.

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