Classifying the Built Environment: Zones, Urbanicity, Transects, and Trends

by Brian Engelmann on 21st May 2012

Each day countless commuters trek through the commuter zone to the CBD, from T3 to T6, from “MSA but not in a central city” to “central city of an MSA,” from residential subdivision to financial district, from sparsely populated to densely populated, and from suburban to urban core. These are just more technical terminologies for describing the prototypical work commute from an outlying bedroom suburb to the center of a nearby city. Commute time from suburb to central city all depends on the size of the city and metropolitan area, geographical barriers, roadway networks, access to mass transit, traffic congestion, and so on. However, commute time may also depend on the amount of land consumed by each degree of urbanicity, or the classification of the landscape by the type of built environment that it holds. Since the built landscape is not a solid continuum, several methods of categorization have been established.

The Reston, Virginia area in Fairfax County via "La Citta Vitta" on Flickr

The built environment houses various building types, densities, networks, land uses, and functions. A typical highway drive into an American urban center from outside of its most far-flung fringe communities begins in the natural areas and rural vistas of forestland, mountains, farmland, and cattle ranches. As the city approaches within the present-day metropolitan area, the landscape begins to show signs of more permanent, non-agricultural settlement patterns. Especially near major highways, residential subdivisions of single-family homes, townhomes, and condominiums emerge in almost random clusters. Next arrives a denser, more continuous type of built environment where a more intense network of roadways and transportation supports tightly-packed rows of single- or multi-family homes, clusters of commercial development, office complexes, and light industry.

Closer to the urban core lies intact street-oriented neighborhoods of high density housing such as rowhouses, mid-rise apartment buildings, mixed-use retail-residential buildings, heavy industry and manufacturing plants, as well as more intensified commercial development. The center of the city boasts an entirely street-oriented class of buildings whose densities far eclipse that of any surrounding areas. Office and apartment towers, heavy industrial uses, transportation hubs, regional government offices and medical care facilities, as well as major entertainment venues make up the core of the urban complex. The core is a major employment, entertainment, civic, transportation and living center wrapped into one incredibly dense central area. In most major cities across America, the entire spectrum of the built environment is

traversed by car in less than an hour. The description just employed is based off of a more recent urban planning model that divides the built environment into six parts. Before that model is revealed, however, it is helpful to understand the beginnings of built landscape classifications and how the urban-rural continuum is defined by government entities.

Concentric Zone Model by Ernest Burgess via "SuzanneKn" on Wikimedia Commons

Concentric Zones, Sectors, and NucleiErnest Burgess of the Chicago School of Sociology pioneered the concentric zone model in 1925. The model was based on the application of natural ecological concepts to human settlement patterns, an idea termed “urban ecology.” Based on his observations of urban areas throughout the U.S., Burgess formulated a land use model for classifying the built environment from central core to suburban fringe. Concentric zones were drawn over a map of the city of Chicago that delineated areas of distinct land uses, socioeconomic characteristics, and geographic distances from downtown. Zone I was labeled the Central Business District, or CBD. Adjacent to the CBD was the factory zone and just beyond that emerged the zone of transition. In Zone III, transition refers to the constant flux of industrial activities amid poor populations living in slum housing and ethnic enclaves. Zone IV housed working class citizens and second generation immigrants at close commuting distance to areas of employment. Zones V and VI were deemed residential and commuting zones, which were generally characterized by low density middle- and upper-class residential communities (Regoli et al., 2010). The concentric zone model is simple, logical, and fit the mold of many American cities prior to proliferation of the automobile.

Homer Hoyt's Sector Model via "Cieran 91" on Wikimedia Commons

Over a decade later in 1939, economist Homer Hoyt introduced the sector model, or Hoyt model, of land use distribution in American cities. According to Hoyt, the land use and socioeconomic classes that Burgess represented as more evenly distributed around the city were instead geographically disseminated in branches or arms of the CBD. Corridors of land use types developed outward from the CBD along major lines of transportation, both commuter and freight. Residential classes were also represented as corridors or individual concentric half-circles. At the crux of Hoyt’s sector model was land use and socioeconomic settlements branching out in various axes along major pipelines of mobility (Rodrigue, 2009).

Following the sector model was an entirely different urban land use distribution model created by geographers Chauncy Harris and Edward Ullman in 1945. In their article “The Nature of Cities,” they proposed a multiple nuclei modelof cities. At the time of the Harris and Ullman model, the presence of the automobile was overwhelmingly felt throughout American cities and was effectively becoming the major mode of transportation. Once restricted to certain parts of the city due to the availability of public transportation, the automobile allowed for the movement of people (those who could afford a car) around the entire metropolitan area to any conceivable destination. This allowed for the formation of pockets of specialized land uses that began to operate as regional centers. Clusters of manufacturing, commercial businesses, and even residential development sprinkled the typical metropolitan area at various distances from the CBD.

Harris & Ullman's Multiple Nuclei Model via "Example" on Wikimedia Commons

Although the automobile had much significance in these distributions, others factors such as cheaper land, access to freight and shipping centers, as well as spatial proximity of similar land uses also influenced the arrangement of land uses and socioeconomic classes in the multiple nuclei model. As mass suburbanization took hold in American cities after the Second World War, the built landscape became even more polarized as areas of monotonous, single-purpose land uses sprawled for miles

UrbanicityUrban land use and transport models are useful for classifying land use and socioeconomic sectors of cities. A more broadly defined classification of the built environment, however, is stimulated from the commonly used words of rural, suburban, and urban. These terms typically denote density and intensity of the built realm rather than individual land use types. The rural-urban dichotomy is best summarized by the term “urbanicity,” coined by W. Allen Martin in 1974, editing author of “The Urban Community,” a collection of key urban sociology, geography, and ecology works. It its most simple form, urbanicity refers to “the degree to which a geographical unit is urban” (Martin). The term, however, captures a categorization of the built

landscape that other words and measurements fail to communicate. While some measures may categorize an entire metropolitan area as urban, the true intention of urbanicity is to break down the metropolitan region into ecological areas of urbanity. In other words, some areas are not as “urban” as others, and thus should be characterized as “suburban.”

Since 1940 the United Nations (UN) compiled reports on urbanization trends throughout the world. The United Nations Population Division continues to use this measurement today, which has undergone criticism due to the lack of universal definitions of urban and rural. For example, the UN maintains data for 228 countries and reports on urbanization trends, but definitions of “urban” vary from country to country where urban may be measured based on administrative boundaries, population size, population density, economic activity, or with no definition at all. To make matters more difficult, the once discernible boundary between urban and rural areas is now blurred by modern suburbanization (which in many developing countries has only recently begun). Grasping urbanization trends worldwide is further complicated by the often dramatic differences in urban development patterns from country to country (Dahly & Adair, 2007). For the purpose of this discussion, however, urban geography in North America will remain the focus.

The Office of Management and Budget (OBM), a federal U.S. agency, began to delineate metropolitan areas in the 1940s and in time for the 1950 U.S. census. Metropolitan Statistical Areas, or MSA’s, were constructed to delineate large centers of population and the adjacent communities that depend on those centers for employment and economic vitality. Micropolitan Statistical Areas are based upon a similar concept, but concern smaller population centers. Both of these classifications lie within the more general Core Based Statistical Areas (CBSA). The units of analyses within CBSA’s are counties, also known as geographic building blocks. Counties are classified as main, central, secondary, outlying, and outside CBSA’s. At the census tract and block level, the U.S. Census Bureau delineates “urban clusters” and “urbanized areas,” both referred to collectively as “urban areas.” Additionally, “Principal cities” are the largest city inside a CBSA and “cores” are densely settled population centers. All of these methods of delineating populated areas are, of course, calculated by using certain stipulations of the population. CBSA’s, for example, are designated based largely upon an “employment interchange measure,” which calculates employment dependencies between adjacent units (Office of Management and Budget, 2010).

As urbanicity becomes an increasingly important measuring tool for social scientists, criminologists, geographers, and federal-level statistics reports, it is reasonable to expect that OBM- and U.S. Census-based classifications such as main counties, secondary counties, outlying counties, and counties outside CBSA’s would be used to substitute for the rural, suburban, urban continuum in country-wide, statewide, or regional studies. Annual national reports such as “Indicators of School Crime and Safety” by the Bureau of Justice Statistics and National Center for Education Statistics use central city of an MSA to define urban areas, inside MSA’s but not in central cities to define suburban areas, and not in MSA’s to define rural areas (Robers et al., 2010).

Urbanicity is broken down into finer scales in the American Housing Survey (AHS), which is conducted by the U.S. Census Bureau every two years and assesses various housing types across different geographies. These geography types include the definition of housing units as either inside or outside CBSA’s. Similar to the “Indicators of School Crime and Safety” report, those housing units that are not in a central city but are located inside CBSA’s are defined as suburban. Population and population density measurements, however, are used to further separate suburban areas into urban suburbs and rural suburbs, using the census-designated “urban areas” and those outside of them (all within CBSA’s). The result is an urban-rural continuum that classifies what are more commonly referred to as cities, inner-ring suburbs, exurbs, and rural areas (Deitz & Siniavskaia, 2011).

Urbanicity in New Jersey from the New Jersey State Police Uniform Crime Reporting Unit, map created by Brian Engelmann

Finally, perhaps one of the most innovative and representative examples of the urban-rural continuum was compiled in a joint effort by the New Jersey Department of Community Affairs, Division of State and Regional Planning, and Bureau of Statewide Planning. The urbanicity distinction is made at the level of municipality and is called “character,” suggesting the character, or spatial distribution, of each town’s built environment. The New Jersey State Police Uniform Crime Reporting Unit uses these classifications in their annual Uniform Crime Report. These categorizations are best described in the words of the report itself:

Urban Center: Densely populated with extensive development. Urban Suburban: Near an urban center but not as extremely developed and more

residential areas. Suburban: Predominantly single family residential, within a short distance of an urban

area. Rural: Scattered small communities and isolated single family dwellings. Rural Center: High density core area with surrounding rural municipalities.

(New Jersey State Police Uniform Crime Reporting Unit, p.5)

While more specific information on how these categories were statistically defined is unavailable, it is evident that state-level agencies in New Jersey have a firm grasp on defining towns by urbanicity throughout the state. When such data is downloaded and connected to Geographic Information Systems, it is evident that the geographic distribution of municipal “character” is visually logical, as New Jersey is sandwiched between the major cities of Philadelphia and New York.

Urban TransectsA sound, visual representation of urbanicity from an architectural and planning perspective is demonstrated through the Urban Transect model, pioneered by Duany Plater-Zyberk & Company in the early 2000s. The transect model is an illustrated version of what urbanicity would most ideally look like based on principals of urban planning, transportation planning, architecture, and community development. It is also used as an official planning tool and is based out of the Center for Applied Transect Studies, which houses a board of directors, technical advisors, and a transect codes council (Center for Applied Transect Studies). The roots of the American city calls back to a time when communities were largely walkable or located within a short walking distance of public transportation. Cities and towns were extremely dense and did not spread over large geographic areas. Traveling from the urban core to farmland or wilderness was usually only a short ride via horse carriage. In order to mitigate the social, environmental, and economic consequences of post-World War II suburban development, towns, cities, and villages must be designed and planned according to the state of the American city prior to the proliferation of the automobile.

A custom Urban Trasect model created by Brian Engelmann. Pictures taken by Brian Engelmann. Information on Urban Transects retrieved from Duany Plater-Zyberk and Company's Urban Transect Model

Thus, the urban transect model embraces the pre-automobile American city and emphasizes high density development at the core with quickly diminishing adjacent densities that lead to rural and natural character over short geographic distances. This intense gradient of building densities over short distances is meant to balance both the natural and manmade environment, to eliminate automobile dependency, to foster sense of community, and to guide building design, among other things. The transect model is arranged by six zones, or “T-zones” for planning purposes. Zone T6 is the “urban core,” T5 is “urban center,” T4 is “general urban,” T3 is “sub-urban,” T2 is “rural,” and T1 is “natural” (Center for Applied Transect Studies).

Urban Transects drawn around Pittsfield, MA. Lines drawn by Brian Engelmann. Source: Google Maps

The diagram of transects presented in this article is meant to visualize the progression of transects through the author’s own pictures of the built and natural environments in New Jersey. Additionally, by drawing lines on Google Maps and using the transect diagrams as visual guides, one can begin to, although subjectively, categorize the built environment by assessing aerial photography. The differences in transect distributions across the U.S. are dramatically illustrated by comparing the small town of Pittsfield, Massachusetts, where the entire transect spectrum is traversed by car in less than 15 minutes, and Atlanta, Georgia, where the transect spectrum from T6 to T2 is difficult to traverse in under a 45 minute drive even without traffic congestion. Official transect diagrams are available through the Center for Applied Transect Studies website.

Urban Transects drawn around Atlanta, GA. Lines drawn by Brian Engelmann. Source: Google Maps

Instead of driving through the urbanicity of a modern-day American city in an hour, the transect model would likely produce a town where the entire spectrum of urbanicity could be traversed on foot in less than half an hour.

The Current State of Cities & Future Trends

With the proliferation of the automobile and post-World War II suburbanization, the urban-rural dichotomy of the traditional American city was interrupted by low-density development of disaggregated land uses over sprawling geographies. The American metropolitan area today is one of many nodes and centers of economic specialization, catering mostly to Harrison & Ullman’s multiple nuclei model of land use and socioeconomic distribution (Rodrigue, 2009). In some metropolitan areas, the number of jobs in suburban areas significantly outweighs that of the central city. With seemingly random clusters of office and condominium complexes sometimes over 40 miles from the central city, it becomes difficult to determine when urban transitions to suburban and when suburban transitions to rural. Mega-region, megalopolis, and other words with the prefix “mega” exhibit the more recent characterizations of the urban environment as metropolitan areas begin to fuse and meld together in giant amalgamations that overlap multiple states.

Dirty sidewalk near an abandoned lot in suburban Houston, via "petit hiboux" on Flickr.

As the urban environment undergoes dramatic and constant changes it becomes particularly important to maintain and improve upon measures of urbanicity for the production of demographics and statistics. These numbers document the changes in populations within various types of built environments and help to guide better development practices and to target poverty alleviation as well as other social problems. Finer scales of urbanicity help to classify the built environment in metropolitan areas where suburban sprawl has eaten up the majority of the landscape. Measuring population characteristics with effective urbanicity scales helps to assess social and economic characteristics by degree of urbanization. In fact, in America’s 95 largest metropolitan areas, suburbs experienced the largest increase in poverty between 2000 and 2008 and in 2008 had surpassed urban areas in total population of those in poverty. Suburbs in these metropolitan areas saw their poor populations grow nearly five times faster than primary cities and also faster than that of non-metropolitan areas (Brookings Institute, 2010). Of the population growth in suburbs from 2000 to 2009, 30 percent was attributed to immigrants. Additionally, foreign-born populations in suburban areas have higher poverty rates than U.S.-born populations (Brookings Institute, 2011).

Throughout the history of American cities, immigrant gateways have almost always flourished in urban centers where foreign-born populations tended to settle in ethnic enclaves and form distinct districts. Today, the city is no longer the only gateway to America. Suburban communities throughout the U.S. are becoming immigrant entryways to various ethnic groups and are experiencing the formation of ethnic enclaves just like cities. And although solid empirical evidence is rather scarce, there is documentation on the movement of populations from suburbs back to urban areas and central cities. More recent generations have demonstrated their preference to live and work in urban environments, have shorter commutes, and have easy access to entertainment, shopping, and basic needs. With the current state of affairs in mind, smart urban planning schemes need to be implemented by way of innovative guidelines such as the Urban Transect model, and detailed accounts of populations characteristics by type of built environment will pave the way for effective social and economic policy improvements as well as targeted and specific urban development schemes.

References

Brookings Institute (2011). Immigration and Poverty in America’s Suburbs. Metropolitan Opportunity Series, Number 14. Brookings Institute.

Brookings Institute (2010). The Suburbanization of Poverty: Trends in Metropolitan America, 2000 to 2008. Metropolitan Opportunity Series, Number 2. Brookings Institute.

Center for Applied Transect Studies. Available from <http://transect.org/index.html>

Dahly, D.L. & Adair, L.S. (2007). Quantifying the Urban Environment: A Scale Measure of Urbanicity Outperforms the Urban–Rural Dichotomy. Social Science & Medicine, 64. 1407-1419.

Deitz, R. & Siniavskaia, N. (2011). The Geography of Home Size and Occupancy: Special Study for HousingEconomics.com. HousingEconomics.com, National Association of Home Builders.

Martin, A. Urbanicity. Available from <http://www.urbanicity.us/>

New Jersey State Police Uniform Crime Reporting Unit. (2011). Crime in NJ for the Year Ending December 31, 2010: Uniform Crime Report-State of New Jersey Trenton, NJ: Office of the Attorney General, Department of Law and Public Safety.

Office of Management and Budget (2010). 2010 Standards for Delineating Metropolitan and Micropolitan Statistical Areas; Notice. Federal Register, 75(123). 37246-37252.

Regoli, R., Hewitt, J., & Delisi, M. (2010). Delinquency in Society (8th ed.). Sudbury, MA: Jones and Bartlett Publishers.

Robers, S., Zhang, J., Truman, J., & Snyder, T. D. (2010). Indicators of School Crime and Safety: 2010 (No. NCES 2011-002/NCJ 230812). Washington, DC: National Center for Education Statistics, Institute of Education Sciences, U.S. Department of Education, Bureau of Justice Statistics, Office of Justice Programs, U.S. Department of Justice.

Rodrigue, J.P. (2009). The Geography of Transport Systems. Dept. of Global Studies & Geography, Hofstra University, New York. Available from <http://people.hofstra.edu/geotrans>