# The Art of Cities/Zoning
## What is Zoning?

Zoning is the term (chiefly utilised in North America) used to the describe the pre-assigned "function" of an area of land by local governments. Zoning allows authorities to designate specific areas which may be used for a particular purpose. For those of you familiar with the PC game SimCity, you will know all about RCI. RCI, short for Residential, Commercial and Industrial, is an abbreviation used to describe the three major zoning categories.
Zoning is the principal reason that you don't find many shopping malls on sleepy cul-de-sacs or mansions beside factories. Using zones forces the three categories together, for organisational purposes as well as common sense, and creates neighbourhoods, commercial districts and industrial estates.
Here are the three RCI zoning categories explained in a little more detail:
* Residential refers to dwellings, either one-family residences or larger buildings such as apartment buildings.
* Commercial describes businesses, almost always offices or retail outlets (shops). Of the three categories, commercial developments are those most likely to be exempt from zoning and allowed to be built alone. This is simply because having all the Wal-Marts or all the petrol stations in one place doesn't make business sense.
However, this page is about the positioning of these zones, their sizes and their impact based on the first two factors.

## Major Zoning Models

| 1 | Outlying residential area |
| 2 | Wealthy residential area |
| 3 | Middle-class residential area |
| 4 | Poor residential area |
| 5 | Industrial manufacturing area |
| 6 | Central business district |
| 7 | Heavy industrial area |
| 8 | Outlying business district |
| 9 | Suburb (separate residential community) |
In the 1920s, a man named Earnest Burgess invented the first true zone model. A zone model is essentially a plan of a common style of zoning, indicating the areas where RCI developments are located and their respective wealth. This not only showed where the buildings were, but also how the wealth was distributed, and explained which zones ended up close to each other as a result of low income. His model showed the major trends in zoning and its impact, all with one simple diagram: the Concentric Ring Model.
The Concentric Ring Model shows that in the centre of most developments is a central business district (CBD), and surrounding that (often separated by a ring of undeveloped land) is a manufacturing sector, under the industrial "umbrella". Of course, not many people want to live near factories, so after that comes low wealth residential development. As one moves further from the central area of activity, the income of residents increases - they have been grouped by the zones. Here is the model on the right, and the legend for all of the diagrams on this page is to the left.
Please note that this is a graphical representation only and does not indicate a perfectly circular street plan!
In the late 1930s, economist Homer Hoyt revised the above model to account for modern transport arteries, and realised that a more realistic zoning model evolving in many cities was not one of relative uniformity but of a more irregular nature, with businesses flowering around transport routes and residences flocking to business. It was this trend which led to the second major zone model in use today.
The Sector Model (shown left) features the same CBD as the Concentric Ring Model, but this time it is completely encompassed by a "poor" residential area, with two opposing branches. To one side of these branches is the industrial area dealing with manufacturing. Note how this undesirable "neighbour" is separated from the higher-end homes by the low wealth areas, so the residential areas 2 and 3 are only next to other houses.
By the end of World War II, many large cities had evolved to take on a new form. While retaining their original CBDs (and relatively similar low-medium-high wealth "bands" radiating from it), they had grown to such a size that one centralised, all-purpose business centre was impractical for several reasons: the lengthy commute from outlying areas, the lack of a focal point for local commerce and the increase in "heavy" industry - highly polluting, particularly undesirable factories. Therefore, the Sector Model was adapted to create the final, and most globally accurate, zone model.
The Multiple Nuclei Model (to the right) shows the typical original layout: CBD, neighboured by manufacturing industries, themselves next to the low-wealth residential zones. Next to that are the medium-wealth homes, and finally the wealthy residences. However, several new aspects have emerged which were not present in the first two models:
* A zone of heavy industry (area 7) on the fringes of the poorer residential areas. When the industries became larger, they were pushed as far from the central areas as possible, settling in the low-wealth zones, where potential employees were abundant and they would not overly damage the economy by eating into the wealthy areas.
* In area 8, a zone appeared which had rarely existed before. It is an outlying business district. When cities became so large that districts were themselves comparable to cities in size, it was clear that a 2-hour daily commute to get to places of work or retail would not suffice, so offices became decentralised: while the CBD still thrived with big multi-nationals, more local businesses shifted their headquarters to outlying areas. New commercial centres were formed, feeding the needs of their individual areas. These specialised, more local "focuses" of communities have become almost global concepts; a standard fixture of most metropolitan areas.
* Perhaps the most important modern zone in any city is the suburb, shown at area 9. Suburbs, which are discussed in greater detail elsewhere in this book, are the ultimate solution to alleviating the pressures of the city: leave it! These very town-like communities are almost completely residential and are usually separate from the main populated area, thrown apart from it by a belt of green, undeveloped land. This almost entirely post-war fixture of cities has reduced the strain both on the city and its inhabitants.
* It is important to note that these models differ in different regions of the world. Wealthy residential areas are usually located on the outlying areas of a city in Anglo-America, whereas in Europe more wealthy areas of a city lie in the center, closer to the CBD.

## Sources

* Three Models of Urban Land Use, University of North Carolina
* Concentric Ring Model, Wikipedia