Built for walking: Cross-city and cross-scale built environment associations with walking from massive, fine-grained mobile trajectory data

Promoting walking is increasingly important for environmental sustainability and public health. This effort requires a nuanced understanding of the relationship between the built environment and walking behavior. Previous studies primarily rely on traditional datasets with limited quantity, resolution, and geographic coverage, restricting cross-scale analysis. This study uses massive, high-resolution mobile trajectory data with trip-level travel mode labels to examine built environment associations with individuals’ choice of walking versus driving across cities and scales. Using data from 5.5 million trips made by 500,000 individuals from three diverse U.S. metropolitan areas in 2022, we comparatively model mode choice as a function of destination built environment factors at both trip and individual levels, within and across cities. We find that destination walkability—measured as the ratio of walkable street network length to total street network length near trip destinations—has consistently strong and positive associations with walking across cities, with heterogeneous effects by income. Built environment factors show scale-specific variation in predictive strength within metropolitan areas. The study provides empirical evidence to support healthy and sustainable mobility, while demonstrating the practical value of massive mobile trajectory data for cross-city and cross-scale travel behavior analysis.