(Photo: “West Village Rooftop,” Dan Nguyen, Flickr)

(Photo: “West Village Rooftop,” Dan Nguyen, Flickr)

Public health can benefit from more compact and connected street networks, which reduce a number of chronic diseases like obesity and heart disease, according to new research.

While it may seem intuitive that environmental factors generally have an impact on health, the link between the physical design of cities and health outcomes has not been fully examined. For example, people in cities with “compact and connected street networks” certainly walk and bike more than people in cities with disparate street networks, but is that a key driver of improved health outcomes?

A new research paper, “Community Design, Street Networks, and Public Health,” by Wesley Marshall of the University of Colorado–Denver, Daniel Piatkowski of Savannah State University, and Norman Garrick of the University of Connecticut suggests that street design may have a larger impact on public health than previously thought.

By studying 24 California cities with an array of street design characteristics and their associated health data, the authors find that living in cities with high intersection density—a measure of compactness—significantly reduces the risk of obesity, diabetes, high blood pressure, and heart disease. A full-grid street pattern also is a factor in lower risk of obesity, high blood pressure, and heart disease, as compared with full treelike patterns.

The authors note that this study differs from other studies that link the physical characteristics of cities and health outcomes because few studies truly capture the differences in street networks. Population density and intersection density are often good indicators of street network design, but they fail to capture the full range of designs. The authors hope that understanding which specific street network designs are associated with positive health outcomes can help drive public policy decisions.

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The authors found that “the fully gridded network—designed with its typical level of compactness, connectivity, and number of lanes on the major roads—would expect a 15 percent reduction in obesity rates, a 10 percent reduction in [high blood pressure] rates, and a 6 percent reduction in heart disease rates, as compared to the standard fully treelike network with its associated design characteristics.”

Even more precise details in street configuration were found to have significant health effects. For example, for a block-group (defined as all the intersections within one square mile) with six-lane major streets rather than two lanes, obesity tends to increase by 29.8 percent; for the wider city, six-lane major streets are shown to increase the instance of diabetes by 366.6 percent. Interestingly, the same six-lane major street on the block level is associated with a drop in heart disease by nearly 29 percent, though it’s unclear why.

Shaping Choices and Future Development

The authors suggest that people should consider the physical structure of their neighborhood and its impact on their health. Even if one has a natural inclination toward living a healthy, active lifestyle, which includes active transportation, the design of a neighborhood’s streets can still adversely affect health outcomes. That is, the physical design of your neighborhood might lessen your desire to walk and bike, even if you are (or want to be) an active walker or cyclist.

The authors also note that it is not too late to ensure that cities and neighborhoods are better designed. They write:

“Researchers estimate that we will build 89 million homes and 190 billion square feet of nonresidential space by 2050. This means that in 2050, we will be able to say that two-thirds of everything in the U.S. was built in just the last 40 years.”

Armed with the knowledge that street design significantly influences health outcomes, the authors hope that smarter design and public policy choices will be made.