Why not build more roads?
Link: http://www.wired.com/2014/06/wuwt-traffic-induced-demand/?mbid=social_twitter
In this article, Adam Mann discusses a thought we’ve all had: why don’t we just build more lanes to alleviate traffic? This obvious answer, it turns out, would actually make traffic worse — as he puts it, “it’s the roads themselves that cause traffic.” Mann discusses induced demand: the idea that increasing supply of something will also increase the demand for it. The fundamental problem with building new roads is that “new roads will create new drivers.” By making it easier to get around, with better roads, we increase the number of trips that people take and the amount that they use their cars. Additionally, better roads in a certain city means increased business interest in that city, which increases the amounts of trucks and shipments in the area. In Paris, where they’ve been systematically decreasing the number and size of roads, they’re noticed a decrease in traffic — some drivers switched to public transportation, and others eliminated trips all together.
This idea is known as Braess’s paradox, which states that if we add extra capacity to a network, we may not improve overall performance because the individual units are acting selfishly, trying to achieve a Nash equilibrium. This connects to our course in various ways. We discussed the idea of traffic as a network on the first day of class, and later spent more time discussing it. Most obviously, we are discussing networks, and the impacts that they have on our lives. When we discuss roads, we’re discussing connectivity at the level of behavior, where the shortest path to work changes based on what everyone else does. Specifically, we’re trying to fix a problem in a network based on information about personal behavior, where we know that all people are going to behave selfishly.