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Braess paradox for new roads? Not all the time….

Have you ever sat in traffic on a major highway and thought to yourself: “hey, I’m smarter than the rest of these people.  I’m going to take X route to save some time.”  You know the alternate route.  In fact, it used to be your normal route, until the highway you’re currently sitting on was built.  Only now, you wish you were off of said highway.  If that’s the case, then you’re part of the negation to the Braess paradox.

As we’ve learned, the Braess paradox is a situation where, with regards to traffic, a new route has been constructed, but travel time and traffic flow actually get worse instead of better.  The Braess paradox does not occur EVERY time a new road is built; however, in cases where it is proven to occur, there are instances where the whole paradox is negated!

Scientists have discovered that as the demand for travel rises, the new route is actually underused, and thus the paradox stops occurring.  Anna Nagurney, professor at University of Massachusetts, Amherst, relates this effect to a phenomenon called “wisdom of crowds”.   In this situation, as the demand for travel gets higher and higher (on a route that normally undergoes the Braess paradox), drivers learn to change their own routes and adapt.  Take the extreme case, for instance; the new road that supposedly should ease traffic flow becomes so crowded and slow, that eventually drivers change their routes, perhaps going back to their old ones.

In fact, the Braess paradox is also found to be negated on the opposite extreme: extremely low traffic.  That is, on a road where the Braess paradox is observed under what may be deemed as “normal” traffic conditions, the same road actually flows well (rather than poorly) under very low traffic levels.  Although this seems logical, it is nevertheless a contradiction to the paradox itself.

This adds a new factor to consider when making editions to a road network in addition to the Braess paradox: in extreme cases, the new route could either be severely overcrowded, or surprisingly underused, resulting in a waste of resources.  This seems to only further complicate the decisions to simply build a road, but it is nonetheless an important finding in the realm of infrastructural networks.

Source Article: Scientist proves Braess paradox ‘disappears’ under high travel demands


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