Walking is often taken for granted or considered as an ancillary activity. Little is known about the distribution of walking in contemporary populations, and even less about the few people who walk for an hour or more in public space on most days of the week, for whom we coined the term "frequent walkers". Because they have succeeded in acquiring and maintaining this behaviour over time, frequent walkers may constitute a pioneer population with the potential to inspire change towards a sustainable and healthy mobility system. This project seeks to understand how and why people become frequent walkers, how they integrate walking into their schedules, and what they perceive as facilitators or hindrances to frequent walking. To answer these questions, we undertook a mixed-methods study with a trans-disciplinary approach. In a quantitative phase, we analysed the Swiss mobility and transport micro-census, finding that the walking is distributed in an unequal manner: over one third of all people aged 6-99 do not travel by foot on a given day, while around 13% walk for 5 km or more. Semi-structured interviews with 41 adult frequent walkers, mostly from the Geneva-Lausanne area, show that concern with personal health, pleasure and well-being are key motivators for walking. Time-management strategies such as getting up earlier in the morning or using alternative routes on the way out and on the way back home are common. Walking is facilitated - but not decisively - by parks or green spaces. Hindrances include road traffic, narrow or missing pavements (sidewalks), slow traffic lights, and exposure to traffic noise, air pollution or tobacco smoke. Environmental motivation is rarely mentioned and we find no trace of an informal community of frequent walkers, who do not know each other and tend to switch off while walking, operating in a socially closed mode. Individual rather than collective motivations emerge from the analysis. We then equipped 48 volunteers with a GPS tracker, for a duration of 8-10 days and carried out computer-assisted follow-up interviews concentrating on the details of walking routes. In an additional phase presented in the Appendix, we enabled a subset of 27 volunteers to have a check-up in the Health Bus of Geneva University Hospitals, to determine their glycaemia, total cholesterol, blood pressure, resting heart rate, body-mass index and waist-to-hip ratio. This phase aimed at acquiring preliminary data for a follow-up project to investigate the health effects of frequent walking. From the pooled analysis, there emerged a group of frequent walkers whose walking was mainly for transport and was integrated into their daily transportation routines. Another group walked for leisure but not for transportation, leading to less favourable impacts on the environment. In our general discussion, we consider frequent walking to be an embodied, situated and inconspicuous practice, with limited instrumental advantages due to the time and effort involved. So-called symbolic attributes, related to perceived status and self-identity, are likely to play an important role and are worthy of future study. We conclude with a research agenda and recommendations for promoting frequent walking at population level.