WISERD Working Paper Series, WISERD/WPS/001

This paper aims to review the state of play of GIS use in measuring accessibility to services drawing on work in areas such as health, public services, transport and environmental justice. The first section describes what is meant by ‘accessibility’ in the context of our research. To date this has predominantly been concerned with measures of geographical accessibility whilst recognising that this forms but one component of a wider notion of access which includes financial, socio-economic and physical measures. We then focus on geographical accessibility to outline some of the key methodological issues that continue to form the basis of numerous studies in this area – including scale of aggregation, distance
metrics used, and the implications of different population assignment techniques. Such issues are illustrated using the floating catchment technique, one of the most popular methods for measuring accessibility in the social science literature over the last decade. We demonstrate its application using the case study of access to public transit in the Head of the Valleys area of South Wales. The paper goes on to describe a research agenda aimed at improving such measures by: incorporating public transport timetables, analysing services of varying quality and characteristics, and measuring access for differing socio-economic groups and alternative (population) demand points. The final section outlines preliminary thoughts on how modelled accessibility measures could be combined with qualitative data to provide a more complete picture of the factors influencing accessibility and how this relates to resident perceptions of access to key public services. In so-doing we highlight the importance of contextualising measures with the daily experiences of residents through Qualitative GIS, and explore new ways in which such data can be integrated through mixed method approaches.