Perspectives

Suburban Sprawl, Body Sprawl

Are Land-Use Patterns Driven by Choice or by the Market?

Perspectives

Suburban Sprawl, Body Sprawl

Are Land-Use Patterns Driven by Choice or by the Market?

URBAN VERSUS SUBURBAN. Congestion, noise, and crime versus open space, quiet, and safer neighborhoods. Such contrasts, along with the growth of high-speed, multilane highways, spawned a massive exodus of families out of U.S. cities and into suburban communities after World War II. More recently, the continuous growth of suburbs — what has come to be known as suburban sprawl — has created a backlash against suburbs, with a new movement of families back into urban cores.

Adherents on both sides of what has become a passionate debate cite quality-of-life issues. Those who favor urban cores often stress the vitality and cultural diversity, while those who favor suburbs often stress the better environment for raising children.

Meanwhile, there is a growing body of research, including a series of studies from the RAND Center for Population Health and Health Disparities, on how “built space” affects our health. One of the pioneers in the field is Lawrence D. Frank, associate professor of community and regional planning at the University of British Columbia. In a visit to the RAND Corporation, he presented results from his latest studies, in which he highlighted not just the link between built space and obesity but also the larger questions about common patterns of land use.

You Can’t Walk There from Here

The key study by Frank focused on individuals living in Atlanta, Ga., which has some of the highest levels of suburban sprawl in the nation. Frank’s study sought to assess the links between where individuals live in Atlanta and the likelihood of their being obese. The study compared self-reported data on body mass index from about 11,000 individuals with objective assessments of the “urban forms” in which they lived.

In terms of urban form, Frank used parcel data to rate the level of land use mix, placing neighborhoods into quartiles based on the mixture of uses — or on “how evenly distributed the neighborhood is between residential, retail, employment, and institutional elements.” At issue is the interconnectivity of the neighborhoods and the access to such things as retail stores, workplaces, schools, and hospitals.

Higher mixed-use areas (more urban) enable people to walk to these locations, while lower mixed-use areas (more suburban) often require people to drive to them. The cul-de-sacs that are such a common feature in suburban developments pretty much force people to drive to “get there from here” (see the figure).

Getting from Point A to Point B Is Tougher Among Cul-de-Sacs Than on a Grid Pattern

Mixed Use, Clear-Cut Results

The results of the study were strikingly consistent. Controlling for age, income, and education, each quartile increase in mixed use was associated with a 12-percent reduction in the odds of being obese.

Results were the most striking for white males. After controlling for sociodemographic factors, the study showed that on average, a 5-foot, 10-inch white male who lived within the lowest quartile of mixed use (in a word, sprawl) weighed 190 pounds versus 180 pounds if he lived within the highest quartile of mixed use (a walkable environment).

Moreover, Frank found that every 30 minutes of driving per day translated into a 3-percent increase in the likelihood of being obese. In contrast, every additional kilometer walked per day translated into a nearly 5-percent reduction in the likelihood of being obese.

Time spent driving increased as “walkability” decreased. (Frank defined “walkability” as mixed land use with high levels of density and street connectivity.) As one would expect, the distances walked increased with walkability. In a more recent study, Frank documented that residents in the most walkable environments in the Atlanta region were 2.4 times more likely to get the recommended daily 30 minutes of moderate physical activity prescribed by the U.S. Surgeon General than were residents of the most sprawling environments of Atlanta. Using activity monitors, Frank found that 37 percent of the residents in the most walkable environments met the 30-minute target, versus 17 percent in the least walkable environments.

Frank was quick to point out that lack of physical activity because of the built environment is only one part of the explanation for obesity; nutrition and the predisposition to active lifestyles also play a role. Still, Frank noted that his results “are consistent with what other studies in the field have shown and that it is encouraging to see independent studies supporting, rather than refuting, one another.”

The Case for Smart Growth

“It’s like going into a grocery store looking for wheat bread and finding only white bread. You buy the white bread because that’s all there is.”

The results make a strong case for “smart growth” — incorporating mixed use — in designing and building communities. But Frank made it clear that his intent is not to tell people where they should live. The real question for Frank is where do individuals want to live? Is there really a demand for suburban living, or is that demand driven by what the marketplace wants to provide?

“It’s like going into a grocery store looking for wheat bread and finding only white bread,” said Frank. “You buy the white bread because that’s all there is. This can be interpreted as a high demand for white bread, when in fact we are just masking the demand for wheat bread.”

There may be more demand for smart growth than is reflected in the building patterns we see. According to another study by Frank, a third of those living on larger lots in Atlanta neighborhoods that are 15–18 miles from work, school, and other important destinations said they would rather live on smaller lots and be closer to those destinations. This finding represents latent demand; as of yet, the supply to meet the demand does not exist.

Based on Frank’s research, it is becoming apparent that the housing market may be, in economic terms, “externalizing” most, if not all, of the health and environmental costs of living in suburban areas. In other words, the market price of suburban housing may be failing to capture, or to internalize, the full costs borne by suburban residents and by society at large.

“It is much cheaper for developers to build suburban communities than it is to build mixed-use ones,” said Frank. And even if developers wanted to build mixed-use communities, the deck is stacked against them. There is not a lot of financing available to do so, and, in many cases, mixed-use areas are designated as illegal by exclusionary zoning restrictions.

Frank finds this ironic, because zoning is predicated on ensuring the health, safety, and welfare of individuals. Based on his studies (and those of others in the field), mixed-use areas might serve the underlying purposes of zoning better than some of the existing zoning laws. square

Related Reading

Health and Community Design: The Impact of the Built Environment on Physical Activity, Lawrence D. Frank, Peter O. Engelke, Thomas L. Schmid, Island Press, 2003, ISBN 1-55963-917-2.
Urban Sprawl and Public Health: Designing, Planning, and Building for Healthy Communities, Howard Frumkin, Lawrence Frank, Richard Jackson, Island Press, 2004, ISBN 1-55963-305-0 (paperback), ISBN 1-55963-912-1 (hardcover).