Urban structure

Urban structure is the arrangement of land use in urban areas. Sociologists, economists, and geographers have developed several models, explaining where different types of people and businesses tend to exist within the urban setting. Three models are described in this article. Urban structure can also refer to the urban spatial structure, which concerns the arrangement of public and private space in cities and the degree of connectivity and accessibility.

Zonal model

This model was the first to explain distribution of social groups within urban areas. Based on one single city, Chicago, it was created by sociologist Ernest Burgess [Burgess E.W. (1924)"The growth of the city: an introduction to a research project" Publications of the American Sociological Society, 18:85-97] in 1924. According to this model, a city grows outward from a central point in a series of rings. The innermost ring represents the central business district. It is surrounded by a second ring, the zone of transition, which contains industry and poorer-quality housing. The third ring contains housing for the working-class and is called the zone of independent workers' homes. The fourth ring has newer and larger houses usually occupied by the middle-class. This ring is called the zone of better residences. The outermost ring is called the commuter's zone. This zone represents people who choose to live in residential suburbs and take a daily commute into the CBD to work.

ectoral model

A second theory of urban structure was proposed in 1939 by an economist named Homer Hoyt [Hoyt H (1939): "The structure and growth of residential neighborhoods in American cities" Washington DC; Federal Housing Administration] . His model, the sector model, proposed that a city develops in sectors instead of rings. Certain areas of a city are more attractive for various activities, whether by chance or geographic and environmental reasons. As the city grows and these activities flourish and expand outward, they do so in a wedge and become a sector of the city. If a district is set up for high income housing, for example, any new development in that district will expand from the outer edge.

To some degree this theory is just a refinement on the concentric model rather than a radical restatement. Both Hoyt and Burgess claimed Chicago supported their model. Burgess claimed that Chicago's central business district was surrounded by a series of rings, broken only by Lake Michigan. Hoyt argued that the best housing developed north from the central business district along Lake Michigan, while industry located along major rail lines and roads to the south, southwest, and northwest.

Calgary, Alberta almost perfectly fits Hoyt's sector model.

Multiple nuclei model

Geographers C.D. Harris and E. L. Ullman developed the multiple nuclei model in 1945 [Harris C D and Ullman E L (1945), "The nature of cities" Annals of the American Academy of Political and Social Science 242: 7-17] . According to this model, a city contains more than one center around which activities revolve. Some activities are attracted to particular nodes while others try to avoid them. For example, a university node may attract well-educated residents, pizzerias, and bookstores, whereas an airport may attract hotels and warehouses. Incompatible land use activities will avoid clustering in the same area, explaining why heavy industry and high-income housing rarely exist in the same neighbourhood.

Road Structure

The arrangement of streets and large thoroughfares in cities can be further divided into various arrangements throughout the different regions of the world. The structure of the roads themselves is usually representative of the dominant culture of the region.

* Europe: A ringed "weblike" structure is typically found in European cities. Medieval European towns were typically constructed around a church or cathedral. Cities founded prior to Christian influence were built around temples and other structures of cultural significance. As such, roads usually radiate outward from this central nucleus. Examples include Rome, which was built around the Colosseum, and Cologne, built around the Kölner Dom.

* North America: A gridlike pattern is common in North American cities, which unlike European Cities, are typically built around a central business district. Early colonial cities such as Boston have a structure that is a hybrid of both the central nucleus structure and the grid structure. In Southwestern Cities such as Phoenix, this grid structure is astoundingly apparent in [http://maps.google.com/maps?f=q&hl=en&geocode=&time=&date=&ttype=&q=Phoenix&ie=UTF8&ll=33.446339,-112.019005&spn=0.144381,0.31929&t=k&z=12&om=0 aerial photographs] of the urban area.

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