Concept of Induced Demand Twisted to Promote Environmental Agenda

The concept of induced demand where widening highways increases the number of cars that use those highways is true. However, some smart growth groups are twisting the concept just to validate a goal. Just because more people will use widened highways, improving highways is not always bad policy. In fact widening highways is often the best solution.

Economic researchers have noted the many benefits from highway construction: enhanced economic activity, reduced travel time in the short-run, decreased greenhouse gas emissions in the short-term, improved safety, etc. State Department of Transportations are very aware of induced demand; in most cases they choose to widen the highway because the economic benefits outweigh the increase in additional traffic. Furthermore, highways can be widened without inducing demand by using pricing or tolling.

Robert Cervero of the University of California-Berkeley proved induced demand was rule on selected California highways. But after Cervero’s research there was a proliferation of studies claiming induced demand where the phenomenon was not happening. The problem was so severe that Cervero wrote a paper pointing out some of the research flaws in these subsequent papers. Yet despite a thorough review and a detailed explanation of what is and what is not induced demand, many of the same groups are making many of the same claims. Streetsblog was up in arms last month with the news that a new freeway in Dallas will not decrease the number of lane miles that are congested. A smart growth ally uncovered the project’s environmental impact statement and because area leaders are not talking to the media, Streetsblog is convinced there is some grand cover-up not seen in Texas since the Kennedy assassination.

Let’s take a look and see what the EIS actually says. It details that between 2013 and 2035 traffic speeds on the corridor are going to increase by two miles per hour and that congestion is going to decrease by 7.1%. Considering Texas’ rapid population growth, decreasing congestion is a significant improvement. And the project has many other benefits. The new highway will provide a fixed reliable guideway for express buses and provide a non-congested alternative to emergency vehicles; with the new lanes buses will not be sitting in traffic. These new lanes will make buses more dependable, increasing bus ridership and likely increasing bus options for commuters, something environmental groups should support. The roadway will increase economic development and tax revenues in the city of Dallas. Further, because it is a tollroad, real induced demand will be limited. In fact one way that traffic on I-30, I-35E and I-45 would really decrease is if the new road were free. Why? Because people are more likely to divert to free roads than toll roads and more likely to take additional trips on these roads.

Does Streetsblog really want more free roads? It seems unlikely. Rather some groups have decided that transit expansion is good and any roadway expansion — free roads, tolled roads, priced roads — is bad. If that is your viewpoint, why let the facts concerning induced demand vs. non-induced demand and their relationship to good public policy interfere?

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