Geographical Access to Services, Health (GASH): Modelling Population Access to New Zealand Public Hospitals

This paper demonstrates a method for estimating the geographical accessibility of public hospitals. Using Geographical Information Systems, cost path analysis is used to determine the minimum travel time and distance to the closest hospital via a road network. This analysis is applied to approximately 36,000 small areas in New Zealand allowing geographical access to be linked to local populations. Statistics can be generated on what is the total time spent traveling or the total distance traveled if everybody visited a hospital once. These statistics can be generated for different management areas and enables comparisons to be made between regions. This accessibility model is intended for decision support for planners assessing the distribution of hospital services. It can also be easily adapted for other services such as access to General Practitioners and cancer screening centers. A difficulty with calculating travel times is determining the travel speeds for different roads. Road layers often contain information that describes the road characteristics and additional information on the bendiness of the roads can be obtained from calculating the sinuosity of the roads. A process for calculating sinuosity and estimating road travel speeds is described. This study has shown that the northern and southern parts of New Zealand have high average travel times to hospital services.