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|The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (August 2013)|
Urban sprawl or suburban sprawl describes the expansion of human populations away from central urban areas into previously remote and rural areas, often resulting in communities reliant upon heavy automobile usage. Urban sprawl is a multifaceted concept of community planning especially relevant to developed nations (and primarily the United States, Canada, and Australia), involving topics that range from the outward spreading of a city and its suburbs, to low-density and auto-dependent development on rural land (which can cause an expansion of the daily urban system), examination of impact of high segregation between residential and commercial uses, and analysis of various design features to determine which may encourage car dependency. The term "sprawl" is most often associated with land use in the English-speaking world; in Continental Europe the term "peri-urbanisation" is often used to denote similar dynamics and phenomena. Urban sprawl has over the last couple of decades become the subject of analysis about how to manage urban growth.
Discussions and debates about sprawl are often made unclear by the uncertainty of the meaning associated with the phrase. For example, some commentators measure sprawl only with the average number of residential units per acre in a given area. But others associate it with decentralization (spread of population without a well-defined centre), discontinuity (leapfrog development, as defined below), segregation of uses, and so forth.
The term urban sprawl generally has negative connotations due to the health, environmental and cultural issues associated with the phrase. Residents of sprawling neighborhoods tend to emit more pollution per person and suffer more traffic fatalities. Sprawl is controversial, with supporters[clarification needed] claiming that consumers prefer lower density neighborhoods and that sprawl does not necessarily increase traffic. Others have argued that sprawl is less a reflection of consumer preferences and more a result of legal structures and court decisions that have encouraged sprawl development.
Urban sprawl has been a feature of cities for as long as they have existed. The dynamic of rich inner city residents moving out to the lower density suburbs of the town can be traced back to Antiquity. Villa suburbunas were a feature of ancient Roman civilization, such as the Roman district of Tusculum where Cicero had his summer house.
The density gradient of industrialising cities has tended to follow a specific pattern: the density of the centre of the city would rise during urbanization and the population would remain heavily concentrated in the city centre with a rapid decline in settlement towards the periphery. Then, with continued economic growth and the expanding networks of public transport, people (particularly the middle class) would then slowly migrate towards the suburbs, gradually softening the population density gradient. This point was generally reached when the city reached a certain stage of economic development. In London, this point was reached in the first half of the 19th century, in Paris toward the end of the century and in New York at the turn of the 20th.
The term "urban sprawl" was first used in an article in the London Times in 1955 as a negative comment on the state of London's outskirts. However, London had been sprawling out of its medieval confines within the City since the 18th century, when the city experienced its' first great urban surge. Areas to the west of Westminster were increasingly built up for the wealthy, to live in the suburbs of the city.
A dramatic increase in the city's urban sprawl began in the 19th century, when labourers flocked from the countryside to work in the new factories that were then springing up. Large developments of small terraced houses began to appear and the new public transportation systems - (the metro, buses and trams) - allowed workers to commute into the city daily. Suburban districts also sprung up around the city centre to accommodate those who wanted to escape the squalid conditions of the industrial town.
By the mid-19th century, the first major suburban areas were springing up around London as the city (then the largest in the world) became more overcrowded and unsanitary. A major catalyst in the growth in urban sprawl came from the opening of the Metropolitan Railway in the 1860s. The line joined the capital's financial heart in the City to what were to become the suburbs of Middlesex. Harrow was reached in 1880, and the line eventually extended as far as Verney Junction in Buckinghamshire, more than 50 miles (80 kilometres) from Baker Street and the centre of London.
Unlike other railway companies, which were required to dispose of surplus land, the Met was allowed to retain such land that it believed was necessary for future railway use.[a] Initially, the surplus land was managed by the Land Committee, and, from the 1880s, the land was developed and sold to domestic buyers in places like Willesden Park Estate, Cecil Park, near Pinner and at Wembley Park. In 1919, with the expectation of a postwar housing boom, the Metropolitan Railway Country Estates Limited (MRCE) was formed and went on to develop estates at Kingsbury Garden Village near Neasden, Wembley Park, Cecil Park and Grange Estate at Pinner and the Cedars Estate at Rickmansworth and create places such as Harrow Garden Village.
By the early twentieth century then, amid increasing middle-class affluence, large low-density suburbs of semi-detached houses had sprung up all around the city, doubling the area of built-up London in the interwar period alone, despite the population increase being just 10 percent. H.G Wells even predicted in 1902 that within a hundred years most of southern England would have been subsumed into one gigantic conurbation centred in London.
Starting in the early 20th century, environmentalist opposition to urban sprawl began to coalesce, with roots in the garden city movement, as well as pressure from campaign groups such as the Campaign to Protect Rural England (CPRE).
Under Herbert Morrison's 1934 leadership of the London County Council, the first formal proposal was made by the Greater London Regional Planning Committee "to provide a reserve supply of public open spaces and of recreational areas and to establish a green belt or girdle of open space". It was again included in an advisory Greater London Plan prepared by Patrick Abercrombie in 1944. The Town and Country Planning Act of 1947 expressly incorporated green belts into all further national urban developments.
New provisions for compensation in the 1947 Town and Country Planning Act allowed local authorities around the country to incorporate green belt proposals in their first development plans. The codification of Green Belt policy and its extension to areas other than London came with the historic Circular 42/55 inviting local planning authorities to consider the establishment of Green Belts. The first urban growth boundary in the U.S. was in Fayette County, Kentucky in 1958.
Sprawl is characterized by several land use patterns that usually occur in unison:
This refers to a situation where commercial, residential, institutional and industrial areas are separated from one another. Consequently, large tracts of land are devoted to a single use and are segregated from one another by open space, infrastructure, or other barriers. As a result, the places where people live, work, shop, and recreate are far from one another, usually to the extent that walking, transit use and bicycling are impractical, so all these activities generally require an automobile.
Sprawl consumes much more land per-capita than traditional urban developments because zoning laws generally require that new developments are of low density. The exact definition of "low density" is arguable, but a common example is that of single family homes on large lots, with four or fewer units per net acre. Buildings usually have fewer stories and are spaced farther apart, separated by lawns, landscaping, roads or parking lots. Lot sizes are larger, and because more automobiles are used much more land is designated for parking. The impact of low density development in many communities is that developed or "urbanized" land is increasing at a faster rate than the population is growing.
Overall density is often lowered by "leapfrog development". This term refers to the relationship, or lack thereof, between subdivisions. Such developments are typically separated by large green belts, i.e. tracts of undeveloped land, resulting in an average density far lower even than the low density described in the previous paragraph. This is a 20th and 21st century phenomenon generated by the current custom of requiring a developer to provide subdivision infrastructure as a condition of development. Usually, the developer is required to set aside a certain percentage of the developed land for public use, including roads, parks and schools. In the past, when a local government built all the streets in a given location, the town could expand without interruption and with a coherent circulation system, because it had condemnation power. Private developers generally do not have such power (although they can sometimes find local governments willing to help), and often choose to develop on the tracts that happen to be for sale at the time they want to build, rather than pay extra or wait for a more appropriate location.
Areas of urban sprawl are also characterized as highly dependent on automobiles for transportation, a condition known as automobile dependency. Most activities, such as shopping and commuting to work, require the use of a car as a result of both the area's isolation from the city and the isolation the area's residential zones have from its industrial and commercial zones. Walking and other methods of transit are not practical; therefore, many of these areas have few or no sidewalks. In many suburban communities, stores and activities that are in close physical proximity require automobiles, because the different areas are separated by fences, walls, and drainage ditches. Some critics argue that excessive parking requirements exacerbate car dependency.
Job Sprawl is another land use symptom of urban sprawl and car-dependent communities. It is defined as low-density, geographically spread-out patterns of employment, where the majority of jobs in a given metropolitan area are located outside of the main city's Central Business District (CBD), and increasingly in the suburban periphery. It is often the result of urban disinvestment, the geographic freedom of employment location allowed by predominantly car-dependent commuting patterns of many American suburbs, and many companies' desire to locate in low-density areas that are often more affordable and offer potential for expansion. Spatial mismatch is related to job sprawl and economic Environmental Justice. Spatial Mismatch is defined as the situation where poor urban, predominantly minority citizens are left without easy access to entry-level jobs, as a result of increasing job sprawl and limited transportation options to facilitate a reverse commute to the suburbs.
Job sprawl has been documented and measured in various ways. It has been shown to be a growing trend in America's metropolitan areas. The Brookings Institution has published multiple articles on the topic. In 2005, author Michael Stoll defined job sprawl simply as jobs located more than 5-mile (8.0 km) radius from the CBD, and measured the concept based on year 2000 U.S. Census data. Other ways of measuring the concept with more detailed rings around the CBD include a 2001 article by Edward Glaeser and Elizabeth Kneebone's 2009 article, which show that sprawling urban peripheries are gaining employment while areas closer to the CBD are losing jobs. These two authors used three geographic rings limited to a 35-mile (56 km) radius around the CBD: 3 miles (4.8 km) or less, 3 to 10 miles (16 km), and 10 to 35 miles (56 km). Kneebone's study showed the following nationwide breakdown for the largest metropolitan areas in 2006: 21.3% of jobs located in the inner ring, 33.6% of jobs in the 3-10 mile ring, and 45.1% in the 10-35 mile ring. This compares to the year 1998 - 23.3%, 34.2%, and 42.5% in those respective rings. The study shows CBD employment share shrinking, and job growth focused in the suburban and exurban outer metropolitan rings.
In terms of measurement, spatial mismatch can be thought of as the percentage of people who would have to move in order to be distributed in the same way as jobs. Stoll's research shows that a substantially higher percentage of African Americans (53.5%) experience spatial mismatch than European Americans (35.6%). On average, more than half of African American citizens would need to move to accomplish similar distribution to jobs. Latinos (45.8%) experience spatial mismatch as well, though to a lesser extent than African Americans.
Land for expansion of suburban housing is usually purchased from farmers and/or ranchers. In the United States the seller may avoid tax on profit by using a tax break exempting like-kind exchanges from capital gains tax; proceeds from the sale are used to purchase cheap agricultural land elsewhere and the transaction is treated as a "swap" or trade of like assets and no tax is due. Thus urban sprawl is subsidized by the tax code.
Housing subdivisions are large tracts of land consisting entirely of newly built residences. Prominent New Urbanist architectural firm Duany Plater-Zyberk & Company claim that housing subdivisions "are sometimes called villages, towns, and neighbourhoods by their developers, which is misleading since those terms denote places that are not exclusively residential." They are also referred to as developments.
Subdivisions often incorporate curved roads and cul-de-sacs. These subdivisions may offer only a few places to enter and exit the development, causing traffic to use high volume collector streets. All trips, no matter how short, must enter the collector road in a suburban system. (Duany Plater-Zyberk 5, 34)
Shopping centres are locations consisting of retail space. In the U.S. and Canada, these vary from strip malls, which refer to collections of buildings sharing a common parking lot, usually built on a high-capacity roadway with commercial functions (i.e., a "strip"). Similar developments in the UK are called Retail Parks. Strip malls/retail parks contain a wide variety of retail and non-retail functions that also cater to daily use (e.g. video rental, takeout food, laundry services, hairdresser). Strip malls consisting mostly of big box stores or category killers are sometimes called "power centers" (U.S.). These developments tend to be low-density; the buildings are single-story and there is ample space for parking and access for delivery vehicles. This character is reflected in the spacious landscaping of the parking lots and walkways and clear signage of the retail establishments. Some strip malls are undergoing a transformation into Lifestyle centers; entailing investments in common areas and facilities (plazas, cafes) and shifting tenancy from daily goods to recreational shopping. European countries such as France, Belgium and Germany have implemented size restrictions for superstores found in strip malls in an effort to limit sprawl (Davies 1995).
Another prominent form of retail development in areas characterized by "sprawl" is the shopping mall. Unlike the strip mall, this is usually composed of a single building surrounded by a parking lot that contains multiple shops, usually "anchored" by one or more department stores (Gruen and Smith 1960). The function and size is also distinct from the strip mall. The focus is almost exclusively on recreational shopping rather than daily goods. Shopping malls also tend to serve a wider (regional) public and require higher-order infrastructure such as highway access and can have floorspaces in excess of a million square feet (ca. 100,000 m²). Shopping malls are often detrimental to downtown shopping centres of nearby cities since the shopping malls act as a surrogate for the city centre (Crawford 1992). Some downtowns have responded to this challenge by building shopping centres of their own (Frieden and Sagelyn 1989).
In the 1970s, the Ontario government created the Ontario Downtown Renewal Programme, which helped finance the building of several downtown malls across Ontario such as Eaton Centre. The program was created to reverse the tide of small business leaving downtowns for larger sites surrounding the city. In the first quarter of 2012 shopping mall private investment hit an all time low under 0.1 percent.
Fast food chains are often built early in areas with low property values where the population is expected to boom and where large traffic is predicted, and set a precedent for future development. Eric Schlosser, in his book Fast Food Nation, argues that fast food chains accelerate suburban sprawl and help set its tone with their expansive parking lots, flashy signs, and plastic architecture (65). Duany Plater Zyberk & Company believe that this reinforces a destructive pattern of growth in an endless quest to move away from the sprawl that only results in creating more of it (Duany Plater-Zyberk 26).
According to the National Resources Inventory (NRI), about 8,900 square kilometres (2.2 million acres) of land in the United States was developed between 1992 and 2002. Presently, the NRI classifies approximately 100,000 more square kilometres (40,000 square miles) (an area approximately the size of Kentucky) as developed than the Census Bureau classifies as urban. The difference in the NRI classification is that it includes rural development, which by definition cannot be considered to be "urban" sprawl. Currently, according to the 2000 Census, approximately 2.6 percent of the U.S. land area is urban. Approximately 0.8 percent of the nation's land is in the 37 urbanized areas with more than 1,000,000 population. In 2002, these 37 urbanized areas supported around 40% of the total American population.
Nonetheless, some urban areas have expanded geographically even while losing population. But it was not just urbanized areas in the U.S. that lost population and sprawled substantially. According to data in "Cities and Automobile Dependence" by Kenworthy and Laube (1999), urbanized area population losses occurred while there was an expansion of sprawl between 1970 and 1990 in Brussels, Belgium; Copenhagen, Denmark; Frankfurt, Hamburg, and Munich, Germany; and Zurich, Switzerland, albeit without the wholesale dismantling of public transit systems that occurred in the United States.
At the same time, the urban cores of these and nearly all other major cities in the United States, Western Europe, and Japan that did not annex new territory experienced the related phenomena of falling household size and, particularly in the U.S., "white flight", sustaining population losses. This trend has slowed somewhat in recent years, as more people have regained an interest in urban living.
Los Angeles was one of the world's first low density urbanized areas, resulting from its large geographic metropolitan area. Today, the area's near universal car ownership makes it a prominent example of sprawl. However, Los Angeles has become more dense over the past half-century, principally due to small lot zoning and a high demand for housing due to population growth. Today, the greater Los Angeles metropolitan area is denser than any other in the country.
Urban sprawl is not limited to developed countries, and may be more prevalent in developing countries. For example, there is considerable land consumed by urban sprawl in Mexico City,in the National Capital Region that surrounds Delhi, in Beijing, the new desert developments of 6 October City and New Cairo to the west and east of Cairo (respectively), in Antananarivo (the capital of Madagascar), in Johannesburg and in eastern parts of South Africa. The international cases of sprawl often draw into question the definition of the term and what conditions are necessary for urban growth to be considered sprawl. In Mexico, for example, new housing development at the urban periphery is single-use but not low-density.
The term 'smart growth' has been particularly used in North America. The terms 'compact city' or 'urban intensification' are often used to describe similar concepts, in Europe and particularly the UK where it has influenced Government policy and planning practice in recent years.
The state of Oregon enacted a law in 1973 limiting the area urban areas could occupy, through urban growth boundaries. As a result, Portland, the state's largest urban area, has become a leader in smart growth policies that seek to make urban areas more compact (they are called urban consolidation policies). After the creation of this boundary, the population density of the urbanized area increased somewhat (from 1,135 in 1970 to 1,290 per km² in 2000). While the growth boundary has not been tight enough to vastly increase density, the consensus is that the growth boundaries have protected great amounts of wild areas and farmland around the metro area.
Many parts of the San Francisco Bay Area have also adopted urban growth boundaries; 25 of its cities and 5 of its counties have urban growth boundaries. Many of these were adopted with the support and advocacy of Greenbelt Alliance, a non-profit land conservation and urban planning organization.
In other areas, the design principles of District Regionalism and New Urbanism have been employed to combat urban sprawl. The concept of Circular flow land use management has been developed in Europe to reduce land take by urban sprawl through promoting inner-city and brownfield development.
These three developments are compatible.
While cities such as Los Angeles are well known for sprawling suburbs, policies and public opinion are changing. Transit-oriented development, in which higher-density mixed-use areas are permitted or encouraged near transit stops is encouraging more compact development in certain areas-particularly those with light and heavy rail transit systems.
Bicycles are the preferred means of travel in many countries. Also, bicycles are permitted in public transit. Businesses in areas of some towns where bicycle use is high are thriving. Bicycles and transit are contributing in two important ways toward the success of businesses:
Walkability is a measure of how friendly an area is to walking. Walkability has many health, environmental, and economic benefits. However, evaluating walkability is challenging because it requires the consideration of many subjective factors. Factors influencing walkability include the presence or absence and quality of footpaths, sidewalks or other pedestrian right-of-ways, traffic and road conditions, land use patterns, building accessibility, and safety, among others. Walkability is an important concept in sustainable urban design.
Arguments opposing urban sprawl run the gamut from the more concrete effects such as health and environmental issues to more abstract consequences involving neighborhood vitality.
Urban sprawl is associated with a number of negative environmental and public health outcomes, with the primary result being increased dependence on automobiles.
In the years following World War II, when vehicle ownership was becoming widespread, public health officials recommended the health benefits of suburbs due to soot and industrial fumes in the city center. However, air in modern suburbs is not necessarily cleaner than air in urban neighborhoods. In fact, the most polluted air is on crowded highways, where people in suburbs tend to spend more time. On average, suburban residents generate more per capita pollution and carbon emissions than their urban counterparts because of their increased driving.
A heavy reliance on automobiles increases traffic throughout the city as well as automobile crashes, pedestrian injuries, and air pollution. Motor vehicle crashes are the leading cause of death for Americans between the ages of five and twenty-four and is the leading accident-related cause for all age groups. Residents of more sprawling areas are at greater risk of dying in a car crash.
Research covered in the Journal of Economic Issues and State and Local Government Review shows a link between sprawl and emergency medical services response and fire department response delays.
The American Journal of Public Health and the American Journal of Health Promotion, have both stated that there is a significant connection between sprawl, obesity, and hypertension. Many urbanists argue that this is due to less walking in sprawl-type developments. Living in a car centered culture forces inhabitants to drive everywhere, thus walking far less than their urban (and generally healthier) counterparts.
Urban sprawl may be partly responsible for the decline in social capital in the United States. Compact neighborhoods can foster casual social interactions among neighbors, while sprawl creates barriers. Sprawl tends to replace public spaces with private spaces such as fenced-in backyards.
Due to the larger area consumed by sprawling suburbs compared to urban neighborhoods, more farmland and wildlife habitats are displaced per resident. As forest cover is cleared and covered with impervious surfaces (concrete and asphalt) in the suburbs, rainfall is less effectively absorbed into the ground water aquifers. This threatens both the quality and quantity of water supplies. Sprawl increases water pollution as rain water picks up gasoline, motor oil, heavy metals, and other pollutants in runoff from parking lots and roads. Sprawl fragments the land, which increases the risk of invasive species spreading into the remaining forest.
Living in larger, more spread out spaces generally makes public services more expensive. Since car usage becomes endemic and public transport often becomes significantly more expensive, city planners are forced to build highway and parking infrastructure, which in turn decreases taxable land and revenue, and decreases the desirability of the area adjacent to such structures. Providing services such as water, sewers, and electricity is also more expensive per household in less dense areas.
Residents of low-density areas spend a higher proportion of their income on transportation than residents of high density areas. The RAC estimates that the average cost of operating a car in the UK is £5,000 a year, most of which stems from financing costs and depreciation. In comparison, a yearly underground ticket for a suburban commuter in London (where the average wage is higher than the national average) costs £1,000-1,500, which, because of subsidies, do not cover financing for the rail or depreciation of the infrastructure. In the Euro-15, rail transit requires $69 billion euro in subsidies while road transportation nets $107 billion euro in additional taxes.
Critics of sprawl maintain that sprawl erodes quality of life. Duany and Plater-Zyberk believe that in traditional neighborhoods the nearness of the workplace to retail and restaurant space that provides cafes and convenience stores with daytime customers is an essential component to the successful balance of urban life. Furthermore, they state that the closeness of the workplace to homes also gives people the option of walking or riding a bicycle to work or school and that without this kind of interaction between the different components of life the urban pattern quickly falls apart. (Duany Plater-Zyberk 6, 28). James Howard Kunstler has argued that poor aesthetics in suburban environments make them "places not worth caring about", and that they lack a sense of history and identity.
Some blame suburbs for what they see as a homogeneity of society and culture, leading to sprawling suburban developments of people with similar race, background and socioeconomic status. They claim that segregated and stratified development was institutionalized in the early 1950s and 1960s with the financial industries' then-legal process of redlining neighborhoods to prevent certain people from entering and residing in affluent districts. Sprawl may have a negative impact on public schools as finances have been pulled out of city cores and diverted to wealthier suburbs. They argue that the residential and social segregation of whites from blacks in the United States creates a socialization process that limits whites' chances for developing meaningful relationships with blacks and other minorities, and that the segregation experienced by whites from blacks fosters segregated lifestyles and can lead to positive views about themselves and negative views about blacks.
The American Institute of Architects and the American Planning Association recommend against sprawl and instead endorses smart, mixed-use development, including buildings in close proximity to one another that cut down on automobile use, save energy, and promote walkable, healthy, well-designed neighborhoods. The Sierra Club, the San Francisco Bay Area's Greenbelt Alliance, 1000 Friends of Oregon and counterpart organizations nationwide, and other environmental organizations oppose sprawl and support investment in existing communities. NumbersUSA, a national organization advocating immigration reduction, also opposes urban sprawl, and its executive director, Roy Beck, specializes in the study of this issue.
American public policy analyst Randal O'Toole of the Cato Institute, a libertarian think tank, has argued that sprawl, thanks to the automobile, gave rise to affordable suburban neighborhoods for middle class and lower class individuals, including non-whites. He notes that efforts to combat sprawl often result in subsidizing development in wealthier and whiter neighborhoods while condemning and demolishing poorer minority neighborhoods.
Peter Gordon, a professor of planning and economics at the University of Southern California's School of Urban Planning and Development, argues that many households in the United States, Canada, and Australia, especially middle and upper class families, have shown a preference for the suburban lifestyle. Reasons cited include a preference towards lower-density development (for lower ambient noise and increased privacy), better schools, less crime, and a generally slower lifestyle than the urban one. Those in favor of the current pro low-density land use policies also argue that this sort of living situation is an issue of personal choice and economic means. One suburban Detroit politician defends low-density development as the preferred lifestyle choice of his constituents, calling it "...the American Dream unfolding before your eyes."
Whether urban sprawl does increase problems of automobile dependency and whether conversely, policies of smart growth can reduce them have been fiercely contested issues over several decades. An influential study in 1989 by Peter Newman and Jeff Kenworthy compared 32 cities across North America, Australia, Europe and Asia. The study has been criticised for its methodology but the main finding that denser cities, particularly in Asia, have lower car use than sprawling cities, particularly in North America, has been largely accepted although the relationship is clearer at the extremes across continents than it is within countries where conditions are more similar.
Within cities, studies from across many countries (mainly in the developed world) have shown that denser urban areas with greater mixture of land use and better public transport tend to have lower car use than less dense suburban and ex-urban residential areas. This usually holds true even after controlling for socio-economic factors such as differences in household composition and income. This does not necessarily imply that suburban sprawl causes high car use, however. One confounding factor, which has been the subject of many studies, is residential self-selection: people who prefer to drive tend to move towards low density suburbs, whereas people who prefer to walk, cycle or use transit tend to move towards higher density urban areas, better served by public transport. Some studies have found that, when self-selection is controlled for, the built environment has no significant effect on travel behaviour. More recent studies using more sophisticated methodologies have generally refuted these findings: density, land use and public transport accessibility can influence travel behaviour, although social and economic factors, particularly household income, usually exert a stronger influence.
Reviewing the evidence on urban intensification, smart growth and their effects on travel behaviour Melia et al. (2011) found support for the arguments of both supporters and opponents of smart growth measures to counteract urban sprawl. Planning policies that increase population densities in urban areas do tend to reduce car use, but the effect is a weak one, so doubling the population density of a particular area will not halve the frequency or distance of car use.
These findings led them to propose the paradox of intensification, which states:
Those not opposed to low density development argue that traffic intensities tend to be less, traffic speeds faster and, as a result, ambient air pollution is lower. (See demographia's report.) Kansas City, Missouri is often cited as an example of ideal low-density development, with congestion below the mean and home prices below comparable Midwestern cities. Wendell Cox and Randal O'Toole are the leading figures supporting lower density development.
Longitudinal (time-lapse) studies of commute times in major metropolitan areas in the United States have shown that commute times decreased for the period 1969 to 1995 even though the geographic size of the city increased.
There is also some concern that Portland-style anti-sprawl policies will increase housing prices. Some research suggests Oregon has had the largest housing affordability loss in the nation, but other research shows that Portland's price increases are comparable to other Western cities.
In Australia, it is claimed by some that housing affordability has hit "crisis levels" due to "urban consolidation" policies implemented by state governments. In Sydney, the ratio of the price of a house relative to income is 9:1. The issue has at times been debated between the major political parties.
There are some sociologists such as Durkheim who suggest there is a link between population density and the number of rules that must be imposed. The theory goes that as people are moved closer together geographically their actions are more likely to noticeably impact others around them. This potential impact requires the creation of additional social or legal rules to prevent conflict. A simple example would be as houses become closer together the acceptable maximum volume of music decreases, as it becomes intrusive to other residents.
Numerous studies link increased population density with increased aggression. Some people believe that increased population density encourages crime and anti-social behavior. It is argued that human beings, while social animals, need significant amounts of social space or they become agitated and aggressive. However, the relationship between higher densities and increased social pathology has been largely discredited