A topography-sensitive 2SFCA approach to measuring accessibility to active living infrastructure and its association with health-enhancing physical activity.

INTRODUCTION: Pedestrian accessibility to neighborhood infrastructure is associated with Physical Activity (PA), yet the built environment is often evaluated as separate facility types, while accessibility measures may not jointly capture population demand and topographic walking burden. This study therefore examined PA in relation to a composite Active Living Infrastructure (ALI) measure that integrates five facility types and applies a Topography-Sensitive Two-Step Floating Catchment Area (T-S2SFCA) model, which weighs facility supply against population demand while adjusting walking distance for slope. METHODS: The model was applied to examine the relationship between pedestrian accessibility to neighborhood facilities and multilevel PA behavior among adult residents in Seongnam, South Korea. Five types of neighborhood amenities-retail, community, public green spaces, public transit, and sports facilities-were conceptualized as a single interdependent ALI system supporting daily mobility, leisure, and structured exercise. Using the proposed T-S2SFCA model, spatial accessibility was calculated across 1,580 residential grid cells at a high-resolution 250 m × 250 m scale. The resulting indices were then linked to cross-sectional survey data (N = 555) and analyzed using multinomial logistic regression across activity levels derived from the International Physical Activity Questionnaire (IPAQ). RESULTS: The empirical findings revealed distinct patterns of association between facility-specific accessibility and PA levels. ALI components were associated with PA at different activity levels. Public green spaces and retail facilities were associated with participation in both activity levels. By contrast, sports and community venues were associated exclusively with Health-Enhancing Physical Activity (HEPA). When integrated, the composite ALI accessibility index exhibited robust positive associations with both minimally active and HEPA levels. CONCLUSION: These results support the systemic conceptualization of ALI and suggest that a neighborhood's capacity to accommodate active living is associated with the synergetic composition and functional complementarity of multiple infrastructure elements working together as a whole rather than with the separate aggregation of isolated destinations. These findings suggest the value of a shift in healthy city planning, away from baseline proximity quotas for individual facilities and toward the coordinated development of cohesive ALI networks that support routine PA across complex terrains.