Density alone does not do much to dissuade car use, research finds

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It seems pretty intuitive that compact urban development would discourage driving. After all, if everything that residents need is close by — from stores and schools to work and education — why use a car?

But new research challenges that premise.

In a just-published article, “Does Compact Development Make People Drive Less?”, the answer seems to be: not necessarily. Mark R. Stevens, associate professor in the School of Community and Regional Planning at the University of British Columbia in Canada, argues that high-density neighbourhoods do lessen reliance on cars — but only by a small amount.

The findings appear in the latest edition of the Journal of the American Planning Association.

Stevens examines two decades of study that has spawned sometimes contradictory conclusions about the impact of dense development on a key measure of driving, the number of vehicle-miles traveled.

His overarching message to planners is two-fold. First, don’t rely on compact designs as the only method to dissuade driving. And second,  don’t assume that this strategy will always work.

Other key takeaways from the article:

  • Planners must understand the realities of compact designs before making claims about anticipated reductions in driving.
  • High-density living only should be assumed to result in modest reductions in driving.
  • ​There are several explanations for variances in academic findings, such as sampling error and selective reporting by researchers of statistically relevant results.

Stevens emphasizes that to lessen car usage and ownership, municipalities must employ other techniques. Some strategies in use around the world include eliminating parking spaces, providing more bike lanes, lowering speed limits, levying congestion charges on cars as they enter urban cores and banning vehicles from some streets.

That’s in addition to introducing new options on the transit side, such as adding and expanding bus-rapid transit, trams, and rail or metro lines.

The conclusions speak volumes about the convenience and allure of personal transportation. Even if a particular neighbourhood is walkable and brimming with public transit, a car still provides other benefits — such as flexibility, immediacy and shelter from the elements — that alternatives may not provide.

And in the United States, Canada and other nations lacking robust inter-city train or bus services, automobiles are often the easiest and fastest way to make trips of a few hours.

Not all academics are in agreement with the assumptions that Stevens has reached. In the same issue of the publication, two other leading specialists in the field strongly refute his analysis.

Reid Ewing, professor of city and metropolitan planning with the University of Utah, and Robert Cervero, professor emeritus of city and regional planning at the University of California, Berkeley, argue that Stevens “has overreached in his conclusions”.

Other professors surveyed by the association provide a mix of reactions. Their feedback ranges from tacit agreement, to the view that there is nothing new here, to the recommendation that planners take the findings to heart.

And Stevens hedges a bit, noting that his study relies on a small sample size, which he acknowledges can lower “confidence” in the accuracy of the results.

You can read up on the whole debate here.

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David Hatch is a correspondent for Citiscope.  Full bio

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