Despite abundant research showing that roadway expansions provide limited congestion relief and increase long-term traffic problems, they still occur due to wishful thinking: advocates claim that “this” project is different.
“Why traffic never gets better,” by David Edmondson is a good discussion of induced vehicle traffic (the additional vehicle travel that results when roadways are expanded), and therefore the futility of using roadway expansions to reduce traffic congestion. “Congestion always wins,” he concludes.
The Fundamental Law of Traffic Congestion states that unpriced roads will always remain congested due to the phenomenon of induced demand. Induced demand is caused by people driving more, additional truck traffic, additional migration, and people switching onto the widened road. These are all economically beneficial, but the benefits of road widening are because congestion returns to the same level, not because congestion is mitigated.
Roadway widening still occurs because of wishful thinking: either that “this” project will be different, or that the short-term benefits will be worthwhile. Matthew Turner, one of the authors of the 2009 study, put it succinctly in a New York Times story last year.
“If you keep adding lanes because you want to reduce traffic congestion, you have to be really determined not to learn from history,” Turner said.
FULL STORY: Why traffic never gets better
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When Will We Believe in Induced Demand?
The well-documented concept has yet to catch on in state departments of transportation, but acknowledging it could dramatically transform U.S. transportation policy.
Failing to Account for Induced Traffic, Even When the Public Demands It
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