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Carmageddon II: Braess’s Paradox Gives LA Hope

In July of 2011, Los Angeles closed a 10-mile stretch of the 405 Freeway for 36 hours in order to do roadwork. Leading up to the weekend of the highway shutdown, people feared the traffic nightmares that were about to take place. The event was often referred to as “Carmageddon” or “Carpocalypse” because everyone expected traffic to be off the charts. However, to everyone’s surprise, traffic was not much of an issue that weekend. In fact, most people got to their destinations faster than usual. One big reason for this is because there were significantly less cars on the road. In a few weeks, the same 10-mile section of I-405 is going to be closed again for 53 hours to do more roadwork.  Since the events of July 2011 were not nearly as bad as expected, people are less likely to listen to the warnings to stay off the roads this time around. Does that mean that the traffic nightmare that we expected last year will finally come to fruition? There’s a good chance the answer is no. But, how is that possible?

I-405 is the most direct way from point A to point B but the amount of people that choose this route causes traffic on a regular basis. People fear that removing this large highway would cause even more traffic because the smaller roads cannot handle this congestion. However, Braess’s paradox suggests that the complete opposite will occur. When I-405 is open, the Nash equilibrium of the traffic distribution is not optimal because too many people choose to drive on this same congested highway. Without I-405, there is a good chance that the traffic will be distributed more evenly across more roadways, causing a decrease in travel times. Although this may seem wildly optimistic, it has occurred in previous situations. One example of this happened on Earth Day in 1990 when New York City closed 42nd street and traffic flow improved. Only time will tell whether or not “Carmageddon II” lives up to its nickname. However, Braess’s paradox gives us hope that a severe traffic nightmare might be avoided once again.

– Greg






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