To reach sustainability transitions, we must learn to leverage social systems into tipping points, where societies exhibit positive feedback loops in the adoption of sustainable behavioural or cultural traits. For instance, future sustainability transitions are often portrayed as having roughly ‘S-shaped’ timelines, introducing pro-environmental lifestyles at an increasingly fast rate until a new sustainable state is reached. However, much less is known about the most efficient ways to reach such transitions, or how self-reinforcing systemic transformations might be instigated through means of policy. This research article models behaviour as the function of the person and their environment. We employ an agent-based model to study the emergence of social tipping points through five interconnected factors which have been previously identified to constitute an ecological approach to human behaviour. These are 1. affordances (action opportunities provided by the physical environment), 2. asocial learning and habituation, 3. personal states (such as intentions and habits), 4. cultural niche construction, and 5. social learning in a social network. Our model suggests that even a linear introduction of pro-environmental affordances to a social system can have non-linear self-reinforcing effects on the emergence of collective pro-environmental behaviour patterns. We also conduct empirical validation with a case study, validating the model against data of the evolution of cycling and driving behaviours in central Copenhagen. Our model gives further evidence and justification for policies that make pro-environmental behaviour psychologically salient, easy, and the path of least resistance.