In the context of population ageing in many developed and developing countries, encouraging active transport behaviors of older adults, is a key public health priority. However, many cross-sectional studies assessing the impact of built environment characteristics on travel behavior fail to address residential self-selection bias, and hence the causal relationship is uncertain. A large-scale public housing scheme provided this study with a unique research opportunity to distinguish residential self-selection from the effects of built environment characteristics on the travel behaviors of older adults (N = 13,468 and 3,961 in two analyses respectively) in Hong Kong, because public housing residents have little freedom to choose their residential locations. The results showed that the elderly living in public housing estates generally have fewer trips, shorter overall travel times and distances, and fewer motorized trips including those by rail or private car than those living in private housing estates. In addition, the results for walking, walking times, numbers of trips, and travel distance for elderly people in public and private housing all exhibited markedly different associations with built environment characteristics. Strength of built environment-travel behavior associations dropped by approximately 30-50% after controlling for the effect of residential self-selection. The results indicate that both built environment characteristics and residential self-selection affect travel behaviors.

Evidence suggests that built environment characteristics affect older adults’ travel activity behaviors, e.g., walking and cycling, which have well-established health benefits. However, the relationship between urban greenery and walking behaviors remains unclear, partly due to methodological limitation. Previous studies often measured urban greenery from a bird’s eye perspective, which may mismatch with the pedestrian’s perception from the street. In this study, we measured greenery view index from eye-level streetscape photos retrieved from Baidu Street View, an online mapping service provider. Walking behaviors of 180 older adults in six neighborhoods were collected from questionnaires. We also measured land use diversity, pedestrian-oriented design (street connectivity), and population density—the three Ds of the built environment. Results show that street greenery view index contributes to walking time of older adults, suggesting street greenery should be taken into design consideration to promote walking behaviors of older adults.

Urban systems exhibit multifractal scaling behaviors arising from their hierarchical and heterogeneous spatial organization. Yet the Green View Index (GVI), a widely used indicator of street-level green visibility, is conventionally measured as a static value, overlooking how green exposure is reorganized across scales, which may bias greening evaluations and planning decisions. This study proposes an “X-minute Greenery” framework to examine GVI as a scale-dependent spatial process. Street view imagery and walking isochrone data from Hong Kong and Shenzhen, China, are integrated to measure GVI across 5, 10, 15, and 20 min walking ranges, while a multifractal-inspired approach is developed to characterize its scale-dependent variation structure. Empirical findings show that (1) GVI variation is not random but associated with urban governance and spatial morphology; (2) a staged pattern of variation is identified, with a GVI level around 0.2 marking an approximate shift in configurations of greening dynamics; (3) even under similar initial GVI conditions, areas can still follow divergent variation patterns across walking scales, exposing latent spatial inequalities aligned with institutional and morphological factors. By framing urban green visibility as a scale-aware complex-systems phenomenon, this study adapts multifractal reasoning to street-level greenery, challenges the “equal green, equal policies” assumption, and supports context-sensitive planning interventions.

Population aging and urbanization highlighted the importance of built environments that support health in later life. This study integrates bibliometric analysis and thematic synthesis to characterize research on the built environment and older adult health and organize evidence on potential health pathways. Bibliometric analysis using CiteSpace covers 2411 publications from the Web of Science Core Collection and China National Knowledge Infrastructure published between 2001 and 2025, comprising 1992 English-language and 419 Chinese-language records. Thematic synthesis draws on selected empirical studies to examine environmental attributes, proposed pathways, and health outcomes. Bibliometric findings identify physical activity, walking, and neighborhood environments as central themes, alongside mental health, quality of life, and community-related concerns.The thematic synthesis organizes the evidence into two complementary pathways: direct physiological exposure, including air pollution and thermal stress, and indirect processes involving physical activity, environmental perception, social interaction, and service use. Density-related evidence suggests that resource proximity, environmental pressure, and mobility demands may shape these relationships across urban settings. The resulting framework highlights the need to consider exposure conditions, practical accessibility, and opportunities for participation jointly. It informs age-friendly planning by linking exposure reduction with accessible daily destinations and supportive public spaces, while recognizing differences in older adults’ capabilities and urban contexts.