A relatively large literature base exists on the use of GIS to measure accessibility in transport studies. Often such research efforts have been conducted as part of wider studies of social exclusion to public transport opportunities. This paper aims to explore the use of floating catchment analysis (FCA) techniques to measure access to public transport opportunities. Whilst FCA methods have been used to measure access to health, employment and leisure services in particular, there have been few studies focused on their potential for measuring access to public transport services. This study builds on previous research concerned with enhancing the FCA methodology to include aspects of proximity to bus stops, the balance between service supply and demand, and cumulative opportunity. We compare FCA-based access measures with both census-derived data and small area geodemographic classifications in order to explore intra-urban variations in accessibility and potential associations with existing socio-economic patterns. Our findings for the city of Cardiff, UK highlight no strong associations with potential measures of social exclusion, and points to evidence that deprived areas within the city are actually better served in terms of the provision of public transport opportunities than some affluent areas. These findings contrast with previous studies which have found disparities between transport supply and social needs. We suggest enhanced FCA measures have real potential in studies of transport-related social exclusion in identifying locations where services should be provided in relation to potential demand as well as in monitoring the implications of placing new routes and access points.