As Americans have moved to automobile-dependent suburbs, vehicle travel has exploded. So as a matter of common sense, it might seem obvious that more sprawl equals more pollution.
This view is backed up by a study conducted by Harvard economist Edward Glaeser and UCLA economist Matthew Kahn [pdf], which found that the least automobile-dependent regions emitted fewer greenhouse gases than other large metropolitan regions. In particular, New York City, the most transit-oriented region in the United States, had the lowest level of automobile-related carbon dioxide emissions among 66 regions surveyed. The five other regions where over ten percent of commuters used public transit (Washington, Chicago, Boston, Philadelphia, San Francisco) also emitted less carbon dioxide than the national median. By contrast, auto-oriented regions such as Memphis had higher-than-average emissions. Moreover, cities consistently created less carbon dioxide than suburbs: in every single one of 66 cities surveyed, transportation-related carbon dioxide emissions (including both emissions from automobiles and emissions from transit) were higher in suburbs than in cities.
Environmental benefits from walkable development are not limited to greenhouse gases. One study by several scholars found if vehicle miles traveled in the 11 largest Midwestern regions decreased by ten percent, the resulting decline in particulate matter pollution would lead to 525 fewer pollution-related deaths and an even larger reduction in the number of hospital admissions. […]