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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Economic & Planning Systems, Inc.
UCLA Lewis Center for Regional Policy Studies
Mpact (formerly Rail~Volution)
Chaddick Institute at DePaul University
City of Piedmont, CA
Great Falls Development Authority, Inc.
HUDs Office of Policy Development and Research