Urban Sprawl

Sprawl is a single-use, low-density, disconnected approach to community design. By separating places where people live, work, and play and limiting direct connections between these activities, sprawl most often renders driving as the only rational travel option. Distances are often too vast, and walking is most often difficult, if not dangerous, in sprawl. Urban sprawl is associated with several adverse health outcomes, including less walking and overall physical activity, increased sedentary time, exposure to air pollution from automobiles, and increased rates of obesity.

Sprawl is one extreme of a continuum of approaches to land development and transportation investment that collectively determine the urban form of an area, which in turn influences the behavior of the residents—for instance, by making it easier or more difficult to include walking in their daily routines. Urban forms range from sprawl that is auto-dependent all the way to smart growth or new urbanist design, which is arguably pedestrian and transit supportive at the expense of reduced auto access. Therefore, sprawl is one of many typologies of urban form along a continuumofautotopedestrianandtransitorientation.

There are several ways in which sprawl has been measured. Typical metrics of urban form includes measures of both the proximity between complementary land uses (residential, shopping, work, entertainment) and the connectivity or directness of travel between locations dedicated to these uses. Proximity is based on the compactness or density and the intermixing of land uses. Another element used to describe urban forms is the design of street networks, which may range from a connected grid to a disconnected cul-de-sac sprawl-type environment. Other measures include the presence of a continuous pedestrian or bike network, crosswalks that are safe and well demarcated, and the placement or setback of development from the edge of a street. These microscale or site-level measures have been less studied but create the character of a place. For instance, an extremely different environment emerges based on whether shops are next to the street or set behind a parking lagoon (large parking lot), a term coined by Howard Kunstler who authored The Geography of Nowhere (1993).

Sprawl is a highly regulated and metered approach to developing land and to investing in transportation, but at a scale that is too vast for the pedestrian: A sprawl environment is designed for movement at 40 miles per hour and is therefore boring to the walker, since walking is relatively static at 3 miles per hour. Sprawl may be better understood in contrast with its opposite, walkability. Where sprawl describes an auto-dependent environment, walkability defines those elements of an environment that support active forms of travel (walking and biking) and public transit and reduce car dependence. A voluminous body of literature has emerged in recent years on the health and environmental benefits of walkability. Research has extended the relationship between urban form (σprawl vs. walkable) and associated travel patterns to vehicle-based air pollution, physical activity, and prevalence of obesity.

There is general agreement at this point that as one moves away from sprawl and toward the walkability end of the urban form continuum, per capita vehicle use, greenhouse gas and air pollutants, and obesity prevalence decline, while walking and physical activity levels increase. More recently, studies are showing significant associations between sprawl, climate change, and per capita energy consumption due to increased auto dependence. It is arguable that this line of reasoning looks at only a part of the relationship between sprawl and climate change. Studies should also evaluate differences in per capita homebased energy consumption due to larger spaces and lack of shared energy sources for heating and cooling in sprawling single family environments—in contrast to the sharing of energy sources that is inherent in multifamily housing.

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