Transport and healthy ageing : understanding causal pathways from metro railways to subjective well-being

Abstract

Population ageing is a global trend that necessitates a re-evaluation of public transport systems and urban environments. In high-density Asian cities, metro railways form the backbone of public transport, significantly influencing the urban mobility, social participation, health, and subjective well-being of older adults. However, older people often perceive barriers to metro use, such as complex navigation and frequent interchanges. The mismatch between their travel behaviour and preferences, coupled with inadequate transport options, can lead to reduced subjective well-being. Despite the significance of this issue, it remains unclear about the impact of metro railways on the well-being of older adults in Asian cites. This thesis aims to delineate the causal pathways linking metro railways to changes in subjective well-being via travel behaviour changes. Using a natural experiment of a new metro line in Hong Kong, I examined these pathways through the mixed-methods approach. I recruited 826 older adults for questionnaire surveys and conducted semi-structured interviews with 148 participants. Participants were assigned to treatment and control groups based on local metro planning knowledge, with the treatment group exposed to the metro intervention. Quantitative analysis involved difference-in-difference (DID) models to assess the effects of the metro intervention on travel behaviour and subjective well-being, and causal mediation analysis to evaluate how changes in travel behaviour mediated the relationship between the intervention and well-being outcomes. For qualitative analysis, I adapted existing theories and frameworks to develop two models: an integrated model combining the transtheoretical model and ecological framework, and a transport-subjective-wellbeing pathway model. These models help the development of interview guides and initial coding frameworks. Thematic analysis provided valuable insights into the process of travel behaviour changes and well-being experiences of older adults following the metro intervention. The findings indicate that the new metro line effectively increased public transport use among older adults, primarily through the creation of new travel demand rather than shifting from other transport modes. This increased use of public transport was linked to significant subjective well-being benefits, especially for those who were already mixed-mode users of both buses and metro services before the intervention. Conversely, older adults who were reluctant to adopt new metro use experienced decreased mobility and well-being. These varied effects can be attributed to the opportunities the new metro provided for accessing new and meaningful activities, which over time enhanced health, social relationships, environmental perception, and independence, ultimately improving subjective well-being. Recognising these substantial well-being benefits, this thesis also identified key facilitators and barriers in the stages of travel behaviour change. This thesis contributes to the literature by exploring the dynamics between metro development, travel behaviour, and subjective well-being. It aims to inspire further research in areas that remain under-explored and offers insights into transport policy. The findings emphasise the importance of considering older adults' subjective well-being in transport planning and promoting diverse public transport options rather than focusing solely on metro-led development. By addressing the specific needs of older people, transport planning can transcend traditional goals and better support active and healthy ageing in Asian cities.