Does subjective wellbeing modify travel behaviour changes among older people in response to a new metro line?

This research aims to estimate how subjective wellbeing at baseline would affect the changes in travel behaviour among older people due to a new public transport infrastructure. Cross-sectional studies have begun to establish the connection between subjective wellbeing and travel behaviour, indicating that a high level of wellbeing can lead to beneficial outcomes such as active mode choice, frequent transport use, and social engagement. To explore this connection further, we conducted a natural experiment with a cohort of 449 older people before and after a new metro line in Hong Kong. Our sample was assigned to the treatment and control groups, with the treatment group exposed to the metro intervention. Difference-in-difference (DID) models were applied to estimate the treatment effects of the metro intervention on travel behaviour changes. Then, we fitted the DID models for wellbeing subgroups to test the effects of three wellbeing dimensions (evaluative, hedonic, and eudaimonic wellbeing) at baseline on the pathways from the new metro to travel behaviour changes. We found the treatment effects of the new metro on travel behaviours were more profound for participants with better subjective wellbeing (p < 0.001). Among the three wellbeing dimensions, eudaimonic wellbeing has the most significant impact on the effectiveness of the metro intervention in producing travel behaviour changes. Our findings revealed that subjective wellbeing might modify the causal link between new transport infrastructure and travel behaviour changes among older people.