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RURAL ACCESSIBILITY
Appendix A Strategic Analysis Methodology
Introduction
The purpose of the strategic analysis which follows is to place the study areas in context, in relation to broader, regional accessibility to major centres and "higher/middle order" services. This is achieved first through an analysis of travel-time to major urban centres, and then by mapping patterns of accessibility to major shopping centres and to key health care facilities. This analysis also points the way to potential development of a type of composite accessibility indicator which may offer a more transparent and easily interpreted alternative to gravity models and "economic potential" 4.
The spatial Framework
The focus of this strategic analysis is not upon local variations in accessibility within the study areas, but upon the latter's position within "broad brush" regional patterns. It is therefore appropriate to devise an appropriate spatial framework of analysis, covering the entire Scottish area at an appropriate level of detail. Ease of geocoding, and the availability of a good range of secondary data (including the recently released 1999 population estimates) suggest that postcode sectors are a useful basic unit.
The first step in devising a spatial framework for rural accessibility analysis is to exclude those postcode sectors which are clearly urban. Many definitions of urban and rural Scotland have been devised over the years. For the purpose of this research it was appropriate to exclude sectors with a population density of more than 2.5 persons per hectare (Figure A1). On this basis 497 of the 950 postcode sectors in Scotland were defined as urban, and excluded from further analysis.
Figure A1: Population Density by Postcode Sector 1999
Since most travel-time analysis is carried out between points rather than polygons, the postcode sectors must be represented by "centroids". Generally speaking "functional centroids" (the largest settlement within each area) are preferred to geographic centroids, (which often fall in sparsely populated parts of the countryside). A set of functional centroids for the 1999 postcode sectors was therefore developed from the list of "settlements" published recently by the GRO. The latter covers all settlements with populations of more than 500 people. 269 rural postcodes were found to have at least one such settlement within their boundaries, and in each case the largest was selected as the functional centroid. The remaining 184 rural sectors had no settlement of more than 500 people within their boundaries, and a geographic centroid was created for each. Figure 2 shows the pattern of rural and urban sectors and their centroids.
Figure 2: Rural Postcode Sector Centroids
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