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Measuring the Development of Urban Sprawl in the US


A team of researchers from the University of Toronto, the Neptis Foundation and the London School of Economics have tracked the evolution of land use in the continental US over time to create a picture of patterns of urban sprawl.

Urban sprawl is widely regarded as an important environmental and social issues, with major implications for the road infrastructure, fuel consumption and emissions. Much of the debate to date, however, has been based on speculation, according to the authors.

The team created a grid of 8.7 billion 30-meter by 30-meter cells and used high-altitude photos 1976 and satellite images from 1992 (the most recent available) to create coverage for the entire US for those two time periods.

The new high-resolution data allow the authors to observe the amount of open space in the neighborhood of every house in every US city. Since development is more scattered when there is more open space around a house, the authors measured urban sprawl by calculating the average amount of open space in the neighborhood of a house in each city.

Among their findings:

  • Los Angeles is less scattered than recent development in Boston.

  • Miami, San Francisco and Los Angeles were the most compact major cities, with Miami being the most compact.

  • Pittsburgh and Atlanta are the most sprawling.

  • Changing the number or size of municipal governments in a metro area has no impact on whether or not urban development is scattered, but controlling access to groundwater does.

  • More recent residential development is not any more scattered than development was in 1976. Forty-two percent of land in the square kilometre surrounding the average residential development in 1976 was open space, compared with 43% in 1992.

They found that while a substantial amount of scattered residential development was built between 1976 and 1992, overall residential development did not become any more biased toward such sprawling areas.

The authors also investigated why some cities are more sprawling than others. They found that a city’s climate, topography and access to groundwater account for 25% of the nationwide variation. When the climate is temperate, people spread out to have more space to enjoy the weather.

Hilly places see more scattered development as people avoid the costs of building on hillsides—but mountains act as a barrier and lead to more compact development. Places with easy access to groundwater see more scattered development, since people can supply remote houses with water by drilling inexpensive wells rather than paying for water lines.

The presence of aquifers is particularly important, and that seems to me to have policy implications. It looks as if controlling access to groundwater is an important way to control whether development spreads or not.

—Matthew Turner, University of Toronto

Roads, on the other hand, have no impact on the extent to which development is scattered, despite commonly held beliefs to the contrary.

We looked at a lot of measures of road density—miles of road per area, average distance to a road, distance to an interstate exit—and we could find no relation between those measures and the scatteredness of development.

—Matthew Turner

One of the common complaints about urban sprawl is that as development spreads, municipal services such as roads, sewers, police and fire protection are more expensive. The authors suggest that this concern is well founded. Development in municipalities that receive larger subsidies from higher levels of government is, on average, more scattered.

People have been eager to rush to policy prescriptions without a very good understanding of the underlying phenomena. We wanted to try to put the policy discussion on sounder footing.

—Matthew Turner

The researchers received funding from the Social Sciences and Humanities Council of Canada, the Centre de Recerca en Economia Internacional and the Centre de Referència d'Economica Analítica and support from the Canadian Institute for Advanced Research and the National Fellows Program at the Hoover Institution.

The team is publishing its findings in the May issue of The Quarterly Journal of Economics, in a paper entitled “Causes of Sprawl: A Portrait from Space.”


  • Maps from Causes of Sprawl



"People have been eager to rush to policy prescriptions without a very good understanding of the underlying phenomena."

Wow. This could be applied to so much more than urban sprawl.

Kudos to them for actually studying a problem rather than merely armchair quarterbacking.


I'm not so sure that their methodology is so reasonable. It implies that the Boston Common (and Central Park) imply sprawl. In fact, they don't -- they've encouraged dense building practices adjacent to valuable city open space.

Consider this another way: lets say you've got clear city blocks -- north/south roads and east/west roads. Lets say each parcel is perfectly square. Now, imagine that every four block "supersquare" has 3 squares dedicated to housing and commerce, and one full square is a city park.

That's a great model for a city, and yet it would show up as sprawl in the model. That isn't sprawl -- that's dense, efficient city planning. Strip malls are sprawl. Left hand turn lanes are sprawl. Acres and acres of parking lots are sprawl.


La less sprawl than New York? Something is wrong here.


LA is thinly spread all over the desert. Nu Yark is all crammed into one tiny island.


They are looking at the distance between buildings? They should overlay population density with what they have.

Lucas- Los Angeles county may be spread out but the City of Los Angeles is not.


Miami is less "sprawling" than New York when you count the entire metropolitan area at issue. The posher NY suburbs on Long Island, Westchester County, New Jersey and Connecticut create a lot of sprawl. Miami versus Manhattan would come out the other way.

I wonder if the following two items made it into their study:

1. Density differential. That is, does their model differentiate between an acre of open land adjacent to a single family house and an acre of open land adjacent to a large multifamily tower, perhaps by dividing that acre by the number of units in the adjacent structure? That way, an amount of open space next to a 50 unit building represents 50 times less sprawl than the same amount of space next to a house.

2. Boundary effect. Both Miami and Los Angeles, two of the three least sprawling cities in this study, have very firm outer borders. Miami is surrounded by the Everglades, and higher (i.e. state and federal) governments have set it aside wildlife preserves and national parks, prohibiting development beyond certain lines, in order to preserve it. Check out Miami using Google Earth and you will see a very sharp development cut-off line. Similarly, in addition to being surrounded by mountains, Los Angeles is surrounded by a large number of legally undevelopable federal lands (again, wildlife refuges, national forests, etc.). A quick glance at a roadmap will reveal that Los Angeles has developed up to the borders of these preserves. San Francisco, of course, is surrounded on three sides by water, and on the fourth by mountains and another swatch of federal land, though the larger Bay Area is more heterogenous. On a similar note, Portland (Oregon) has instituted an Urban Growth Boundary (in coordination with state government, to prevent suburbs leapfrogging municipalities) and is also reputedly avoiding sprawl.

Boston, Atlanta and Pittsburgh, by contrast, are not completely surrounded by legally untouchable land, so as inner portions more fully densify, developers can keep pushing outward to develop the fringe at low density. Forty years ago, the Route 128 loop (a limited access highway which orbits downtown at ten mile radius) was considered remote and highly suburban. Now, a large number of big office parks (many containing high-tech firms) lie near the exits of that highway, and developers have been putting in low-density suburbs out by the 495 loop (twenty mile orbit) where commuters headed for the 128 office parks can live.

A final lesson is that being one of the top non-sprawling cities has little to do with walkability, quality of public transit, and environmental friendliness. Having grown up in Miami, I can assure the readers of this post that public transit was (and remains) rudimentary there. Everyone drives. And I don't have to talk about LA. Meanwhile, someone who wants to avoid driving could probably do better by moving to the right neighborhood in Boston or New York and taking the subway to work in the morning.

tom deplume

I wonder how much their conclusion about the lack of influence the Interstate highways have had if they had used 1956 as their starting point. By 1976 most of the Interstate system was already in place. A good measure of sprawl would be the incease in lane-miles of outlying roads. Around Grand Rapids most new road construction has been the widening of roads. Also places where we regularly shop now were places where my brother regularly hunted back in the 60s.


I don't think this accurately depicts the highway/lane extensions to urban sprawl. Personally I've seen this happen in and around Toronto. Hwy 400 was a one lane highway beyond Major Macinzie exit, it is now a four lane highway as the developers pushed the government in building this lane extensions. As a result, they were able to build thousand's of new houses between 1998 and now. The same goes to Hwy 401 beyond Scarborough. Another example is the toll higway 407 that was build to connect these new developments (north of Toronto). No one would move out of the City (there are always few exceptions) and spend hours in their car if there is going to heavy congestion entering the city. As a result, 401 is a mess, by those who come from all these newly built highways, as it is the only artery that carries millions of riders inside toronto. 403 is also another example...

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