5.5 Generalized models – ARIA

Australia is a country which poses particular challenges in terms of health care accessibility. The population is extremely sparsely distributed across a vast land area, resulting in very low population densities across most of the country. Principal population centres are focused on major coastal cities. Accessibility to services, particularly in rural areas, is therefore a key issue for planning in many fields including health care. In response to the need for generally-available accessibility information the Accessibility and Remoteness Index of Australia (ARIA) has been developed by researchers at the University of Adelaide as a general purpose accessibility index, which has seen particular application in the health sector.

The index, and the more recent ARIA+ index are based on a geographical measure of remoteness from population centres of various sizes. Distances along the road network are used to assess the distances of 11,879 populated localities to service centres defined as populated localities classified into groups by population size. The concept is not to measure the distances from specific facilities such as hospitals or general practices but to provide a generalised index of distance from service centres of successive population sizes and to express these relative to the national mean distance for each category. The rationale is that centres of a given population size will generally provide a similar portfolio of services and that a measure constructed in this way provides a more robust and general-purpose index. These standardized scores are then combined into an overall ARIA score. The scores at all populated localities are then interpolated onto a grid in order to produce maps for the whole of Australia and maps of the resulting index can be viewed online. The ARIA website also outlines the methodology.

Health applications of the ARIA index include specific adaptations of the index for GP and pharmacy services. For example, Bamford et al. (1999) illustrate a simple application of the original ARIA methodology in order to accessibility of GP services and Cancer Council for New South Wales (2002) considers the potential influence of remoteness on access to cancer screening services. Moorin and Holman (2006) consider accessibility using ARIA alongside other factors which may influence patient hospital use.