Density Is Not A Cost-Effective Solution To Traffic Congestion!

COST Commentary This is a posting in this series of articles which contrast transportation realities with perceptions and promotions of many. Austin and many similar U.S. cities, developed after the introduction of the automobile, are pursuing density as a major solution to traffic congestion with the theory that if people live in higher density, they will drive less resulting is reducing congestion. There are many previous COST postings and comments that this approach has no success models and that the reverse is actually true: the higher the density, the greater the congestion. Basically, higher density may result in slightly less driving per person, but the increased number of people result in more driving in the area, causing greater congestion.

A new research study, by Professors at the University of Pennsylvania (Wharton School) and Brown University confirms this reality with one of the more thorough analysis we have seen. However, COST does not totally agree with the research study’s authors regarding suppositions which have nothing to do with the major research conclusions regarding the relationship between density and driving.

This papers conclusion is: “In sum, while dense urban development may well be desirable because it provides a residential environment where people want to live and that make them work more productive (e.g., Rosenthal and Strange, 2008), it is probably more costly to manipulate driving behavior through densification policies than through congestion pricing or gasoline taxes.” (bold highlighting added by COST)
Below is a Knowledge@Wharton introduction to its shorter discussion of the very technical, full research paper which is referenced below the Knowledge@ Wharton summary:

Feb 09, 2016, Knowledge@Wharton

As urban areas become more congested, and concerns over the environmental damage that can be caused by vehicle emissions grow, many municipalities are adopting land use guidelines that encourage compact development. A city with greater density, they theorize, will reduce the need to drive by bringing services and retail closer to the areas in which people live.

But new research co-authored by Wharton real estate professor Gilles Duranton finds that such policies may not have as great an effect as planners believe. In “Urban Form and Driving: Evidence from U.S. Cities,” Duranton and Brown University professor Matthew A. Turner find that increases in density cause only minimal decreases in aggregate driving, meaning it is unlikely to be a cost-effective policy for responding to traffic congestion or automobile-related pollution.

Duranton recently talked with Knowledge@Wharton about their findings and how they might be applied by businesses or governments.
An edited transcript of the conversation appears below.

Why Better Urban Planning Won’t Reduce Traffic — but Taxes Will

Full research paper:
Urban form and driving: Evidence from US cities:

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