Urban Traffic: More Roads Don’t Mean Less Traffic

It is estimated that by 2030 the cumulative cost of traffic congestion in the United States will reach 2.8 Trillion Dollars. The usual way we have responded to this situation is build more highways and roads. However, as Adam Mann, an Angeleno points out in his article, building more lanes on the 405 has not helped whatsoever. This is due to what economists call induced demand where once we increase supply of something such as freeways, it only makes more people want to use those freeways. Then what should we do about our growing traffic problem in major cities? One radical solution that Adam discusses is to actually  remove certain roads, not build additional highways, and generally reduce the amount of roads. *gasp* But isn’t this counter intuitive? It is, and when the news of removing lanes on a highway spreads to citizens it is usually ill received. However,  Network Game Theory and Braess’s Paradox perfectly explains this interesting situation.

In 1968, Dietrich Braess articulated a phenomenon “that adding resources to a transportation network can sometimes hurt performance at equilibrium (http://www.cs.cornell.edu/home/kleinber/networks-book/networks-book-ch08.pdf, 232). In other words, building more roads, highways, etc. in certain situations could actually increase the total travel time of commuters as new “fast” roads will draw all commuters to them which negatively affects the entire network.

Due to this phenomenon removing  certain roads will change traffic patterns to a point where many commuters will think of alternate ways of transportation that are more convenient to them (Game theory!). This includes taking alternate roads, taking the bus, using the subway, or even walking!

As the government of Seattle is planning to remove the Alaskan Way Viaduct they have published a study which includes six instances where removing major roads of transportation has been beneficial. In fact, not only has removing major roads of transportation lessened road traffic such as that in San Francisco or Seoul but also freed up land for renovation and clean-up. So the next time when you hear the government is pouring money into new roads don’t always think it will help solve the problem. Instead look to eliminate roads that would alter the traffic patterns so the new equilibrium is beneficial to all.

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