A new concept of accessibility to personal activities: development of theory and application to an empirical study of mobility resource holdings

Abstract The notion of spatio-temporal accessibility to [potential] out-of-home activities is central to transport geography. This paper extends existing theory by proposing a new concept of accessibility, termed the ‘perceived activity set’ (PAS). A person’s PAS is defined as the set of out-of-home activities which they view as encompassing their potential travel needs when making decisions that structurally affect their accessibility. In other words, it is proposed that a person’s mobility-linked choices such as, for instance, where to live or whether to own a car, are a function of how such choices affect their ability to access out-of-home activities they consider relevant. This paper first formalises the PAS and places it in the wider context of accessibility theory. It then presents an empirical study that makes use of the PAS concept, which analyses people’s ownership of several mobility resources that each enable particular forms of travel. The PAS appears promising, as it unlocks a class of flexible techniques that relax restrictive assumptions regarding the drivers behind structural choices related to personal mobility. The techniques were found to be analytically tractable, and the empirical analysis based on the PAS yielded a number of insights. The advantages of using long-duration diaries with PAS-based techniques, rather than more-common one-day diaries, are shown to be large. It was found that the more ‘substantial’ a mobility resource is (in terms of expense and commitment) the better the PAS concept is at explaining patterns of ownership. The paper concludes with suggested directions for research to further develop the PAS concept, which include refinements to the quantitative techniques, extension to other structural mobility choices, and qualitative research into the nature of the relationship between people’s perceived needs for mobility and their expected activity patterns over longer periods than are observed by most activity and travel surveys.