Background Life events, including residential relocation, have been identified as potential triggers of behaviour change and reconsideration of travel. Previous research has indicated that movers are distinct in their demographic, socio-economic, and behavioural characteristics, as well as their perceptions of the environment they live in. Yet, the exact process that leads newcomers to change their behaviour after moving is not well understood.

Methods Employing a novel Theory Building Process Tracing approach, we conduct a secondary analysis of 144 face-to-face interviews held between 2008 and 2011 in twelve Cycling Cities and Towns (CCTs) in England. This qualitative study focuses on the impact of relocation on behaviour, specifically in transport and leisure activities. Contextual mechanism and their parts are traced to explore triggers, barrier, and facilitators for travel behaviour changes and contextual factors influencing these shifts. Moving from evidence to mechanisms to theory we built upon the detailed within case analysis to form generalisable processes and theories of change.

Results We unveil several distinct causal mechanisms between relocation and travel behaviour changes, operating through e.g. changes in norms, changes in access, and changes in time. It is shown that the intricate within-case processes are reproduced in different participants, creating a multi-layered decision-making map. Intriguingly, life events such as having a child, uniting households, or changing jobs trigger similar behaviour change mechanisms, even without relocation. Partner presence emerges as a vital contextual factor enabling active travel modes, while positive social reinforcement amplifies many mechanisms. Additionally, we identify beliefs, interest, access as necessary prerequisites for most causal mechanisms.

Conclusion This study offers a comprehensive understanding of the relationship between residential relocation and changes in travel behaviour. Our findings are valuable for updating current assumptions about newcomers’ attitudes and characteristics including residential self-selection bias and the healthy mover hypothesis, as well as informing how to purposefully shift behaviours e.g. transitioning from car to active travel. Additionally, the insights offering valuable perspectives for predicting movers behaviour and assessing the impact of internal migration for urban planning. Theory Building Process Tracing is found to be a very applicable and insightful method for exploring behavioural determinants of health and understanding how changes occur.