In prior research, Marshall told me, they found that in the most extreme cases “older, denser, connected cities were killing three times fewer people than sparser, tree-like cities on an annual basis." Of course, people walk and bike more in dense cities, but the research on actual ties to health outcomes is scant. So Garrick and Marshall, along with Daniel Piatkowski at Savannah State University, took on and have just completed a large study of how street networks might influence our health.
They looked at the three fundamental measures of street networks—density, connectivity, and configuration—in 24 California cities, and compared them with various maladies. In the current Journal of Transport and Health, Garrick and Marshall report that cities with more compact street networks—specifically, increased intersection density—have lower levels of obesity, diabetes, high blood pressure, and heart disease. The more intersections, the healthier the humans.
“It might not be common for people to explicitly contemplate health when selecting a place to live,” Garrick and Marshall write, “but this research indicates it is worth considering.”
And people are starting to consider it.
The original city design was really no design at all. Known as “organic,” it is the medieval pattern we see throughout many of Europe’s haphazardly still-thriving cities. Then, for centuries during and after the Renaissance, the rectilinear grid was the gold standard in city design. But in the twentieth century came what Garrick and Marshall call a complete overhaul—a shift toward the branching tree model of the modern subdivision, which was optimized for the great horseless carriage.
|Three street networks: Organic (Seville), grid (midtown Manhattan), and hierarchical (suburban Atlanta) (Frank et al., Health and Community Design)|
|Healthiest city designs, from best to worst|
(Journal of Transportation and Health)
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