Scheduled public transport data has been used extensively for estimating travel times in measuring accessibility to a wide range of services by alternative modes of transport. However, fewer studies to date have investigated the implications of using real-time travel data versus transit schedule data to investigate spatial patterns of accessibility. The overall aims of this study are to display the potential uses of live transit data that can be used to examine the accessibility differences introduced by using open data sources of real-time traffic data. Drawing on case studies for Cardiff and Swansea, the aim is to explore the implications of differences between scheduled and actual bus provision for accessibility to POIs in the respective cities. We conclude by suggesting that such impacts are often overlooked when using scheduled timetable data in accessibility analysis.