Equity of access to tertiary hospitals in Wales: a travel time analysis.

BACKGROUND: The objective of the study was to investigate the implications for equity of geographical access for population subgroups arising from hypothetical scenarios of change in configuration of National Health Service tertiary hospital service provision located in Wales.
METHODS: For each of three scenarios, the status quo and centralization of services to one of two locations, we used a travel time road length matrix in geographical information software to calculate the proportion of the population living within 30, 60, 90 and 120 min travel of each hospital site and the associated mean, median and 90th percentile travel times. We analysed data for the total resident population of Wales, for residents aged 75 or more years, for residents of the most deprived 10 per cent of enumeration districts, and for residents of rural areas.
RESULTS: Centralization of services reduces geographical access for all population subgroups. Access varies between population subgroups, both between and within different scenarios of service configuration. A change in service configuration may improve access for one subgroup but reduce access for another. The interpretation may also vary according to whether the defined cut point for comparing access is based on short or long travel times. Measurements of absolute and relative access are sensitive to the assumed travel speeds.
CONCLUSION: Access for the total population does not imply equity of access for subgroups of the population. Comparisons of access between scenarios are dependent on which measure of access is the indicator of choice. Results are sensitive to the road network travel speeds and further local validation may be necessary. This method can provide explicit information to health service planners on the effects on equity of access from a change in service configuration.