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Braess’s Paradox ‘disappears’ under high traffic demands: The “Wisdom of Crowds” in transportation networks.

As we have seen in lecture, adding a new road in some traffic areas may result in equilibrium at which the individual driving times increases instead of decreasing. This phenomenon, called the Braess’s Paradox, may sound counter-intuitive to most people, especially to traffic engineers who thinks that more roads equals less traffic. Formulated in 1968 by Dietrich Braess, the paradox has drawn an increasing attention by scientists. However, in the past couple years, scientists have been reconsidering and reanalyzing the paradox in different conditions. And in a recent interesting finding, scientists showed that the paradox stops happening when the demand for traffic increases.

Professor Anna Nagurney, University of Massachusetts Amherst, proved that a new road will not be used in the case of a very high traffic, thus not resulting in a delay in the driving time. This effect is attributed to the “Wisdom of Crowds” pheromone. Generally we think about the drivers whose behavior is to optimize their individual driving times as the core problem in Braess’s Paradox; however, the “Wisdom of Crowds” pheromone suggests that a sufficiently large group of drivers with the above behavior may somehow contribute to optimizing the travelling time for the entire system. Drivers in a very high travel demand areas eventually learn to switch from particular roads that add so much travel time to other roads; therefore, roads where Braess’s Paradox may occur get abandon over time.

This new results just add more complexity to the problem of traffic control, especially in huge cities. Now, traffic engineers wishing to add a new road should not only be worried about whether the new road will increases individual driving times, but they should also take into consideration that the new road might eventually not be used at all due to the “Wisdom of Crowds” pheromone – the latter case would just mean wasting the money of the city.

 

Attached is a link from Phys.org website that includes an article talking about Braess’s Paradox and the “Wisdom of Crowds” pheromone in a more depth.

http://phys.org/news203665202.html

– haa54

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