Investigating highly contextual behaviours, such as travel choices or health activities, can benefit from automated data capture using GPS, but also require self-report of actions and intentions. We present a case study of how event-based micro-surveys can be combined with GPS to understand car sharing behaviour. An opportunity sample of 24 participants took part in a seven-day study. At the
... [Show full abstract] start of each journey, participants used a smartphone-based application to provide basic self-report information about their journeys and their amenability to sharing. The application then tracked their journey giving a GPS trace for distance, time and duration. The combined micro-survey and GPS approach gave useful data relating whether journeys were shared, whether they could be shared, and some of the characteristics of those journeys. This supported exploratory analysis and hypothesis testing. However, usability of the application was a major consideration in the acceptability of the study, particularly with regards to the design of open questions. Also, the time sensitive nature of contextual behaviour means there is a trade-off between the depth of data captured by micro-survey, and survey completion. Overall, while we find there is empirical value in the combination of micro-survey and GPS, application usability, and appropriate design to reflect the behaviour under study are major factors in the success of this approach.