thumb|right

Central place theory is an urban geographical theory that seeks to explain the number, size and range of market services in a commercial system or human settlements in a residential system. Introduced in 1933 it aims to illustrate how settlements locate in relation to one another, considering the size and distribution of 'central places.' The theory was first analysed by German geographer Walter Christaller, who asserted that settlements simply functioned as 'central places' providing economic services to surrounding areas.

All areas have:

  • an unbounded isotropic (all flat), homogeneous, limitless surface (abstract space)
  • an evenly distributed population
  • all settlements are equidistant and exist in a triangular lattice pattern
  • evenly distributed resources
  • distance decay mechanism
  • perfect competition and all sellers are economic people maximising their profits
  • consumers are of the same income level and same shopping behaviour
  • all consumers have a similar purchasing power and demand for goods and services.
  • Consumers visit the nearest central places that provide the function which they demand. They minimise the distance to be travelled
  • no provider of goods or services is able to earn excess profit (each supplier has a monopoly over a hinterland)

Therefore, the trade areas of these central places who provide a particular good or service must all be of equal size

  • there is only one type of transport and this would be equally easy in all directions
  • transport cost is directly proportional to distance travelled

The theory then relied on two concepts: threshold and range.

  • Threshold is the minimum market (population or income) needed to bring about the selling of a particular good or service.
  • Range is the maximum distance consumers are prepared to travel to acquire goods — at some point the cost or inconvenience will outweigh the need for the good.

The result of these consumer preferences is that a system of centres of various sizes will emerge. Each centre will supply particular types of goods forming levels of hierarchy. In the functional hierarchies, generalisations can be made regarding the spacing, size and function of settlements.

  1. The larger the settlements are in size, the fewer in number they will be, i.e. there are many small villages, but few large cities.
  2. The larger the settlements grow in size, the greater the distance between them, i.e. villages are usually found close together, while cities are spaced much further apart.
  3. As a settlement increases in size, the range and number of its functions will increase .
  4. As a settlement increases in size, the number of higher-order services will also increase, i.e. a greater degree of specialisation occurs in the services.

The higher the order of the goods and services (more durable, valuable and variable), the larger the range of the goods and services, the longer the distance people are willing to travel to acquire them. Although, higher goods can increase the price of lower goods or knock off versions of the higher goods.

At the base of the hierarchy pyramid are shopping centres, newsagents etc. which sell low order goods. These centres are small. At the top of the pyramid are centres selling high order goods. These centres are large. Examples for low order goods and services are: newspaper stalls, groceries, bakeries and post offices. Examples for high order goods and services include jewelry, large shopping malls and arcades. They are supported by a much larger threshold population and demand.

Predictions

He deduced that settlements would tend to form in a triangular/hexagonal lattice, as it is the most efficient pattern to serve areas without any overlap.

Making central place theory operational

CPT is often criticised as being "unrealistic". However, several studies show that it can describe existing urban systems. An important issue is that Christaller's original formulation is incorrect in several ways (Smith). These errors become apparent if we try to make CPT "operational", that is if we try to derive numerical data out of the theoretical schemata. These problems have been identified by Veneris (1984) and subsequently by Openshaw and Veneris (2003), who provided also theoretically sound and consistent solutions, based on a K=3, 37-centre CP system:

  1. Closure problem. Christaller's original scheme implies an infinite landscape. Although each market has finite size, the total system has no boundaries to it. Neither Christaller, nor the early related literature provide any guidance as to how the system can be "contained". Openshaw and Veneris (2003) identified three different types of closure, namely (a) isolated state, (b) territorial closure and (c) functional closure. Each closure type implies different population patterns.
  2. Generating trips. Following the basic Christallerian logic and the closure types identified, Openshaw and Veneris (2003) calculate trip patterns between the 27 centres.
  3. Calculating inter- and intra-zonal costs/distances. Christaller assumed freedom of movement in all directions, which would imply "airline" distances between centres. At the same time, he provided specific road networks for the CP system, which do not allow for airline distances. This is a major flaw which neither Christaller, nor early related literature have identified. Openshaw and Veneris (2003) calculate costs/distances which are consistent with the Christallerian principles.

Central place theory and spatial interaction models

It was once thought that central place theory is not compatible with spatial interaction models (SIM). It is paradoxical however that some times towns or shopping centres are planned with CPT, and subsequently evaluated with SIM.

Openshaw and Veneris (2003) succeeded in linking these two major regional theories in a clear and theoretically consistent way: using the data they derived from the operationalisation of CPT, they experimented with several SIM. Following a thorough investigation via computer simulation, they reached important theoretical and practical conclusions.

Smith was able to delineate medical care regions (the range), describe the hierarchy of medical services, the population base required of each medical specialty (threshold), the efficiency of regions, and the importance of how an area was settled to the delivery of medical care, that is, according to traffic, market or administrative principles.

See also

  • Demographic gravitation
  • The City (Weber book)
  • Fractal
  • Penrose tiling
  • Zipf's law
  • Boundary problem (in spatial analysis)
  • Unified settlement planning

Notes

References

  • Walter Christaller's Theory of Central Places
  • Christaller's Central Place Theory
  • Christaller — Course notes
  • Central Places Theory