Strategic Complementarities and Coordination Failures in Urban Active Transport: Game-Theoretic Evidence from 33,054 Chicago Census Blocks

Why do some urban neighborhoods walk while others drive, even when their physical environments appear similar? This study demonstrates that travel mode choice is fundamentally a coordination problem rather than an infrastructure capacity problem. Using a game-theoretic framework calibrated directly from observed commute behavior across all 33,054 census blocks in Chicago, we show that neighbors’ walking behavior exerts a dominant influence on individual mode choice—outweighing the combined effects of density, safety, land use, and accessibility. We estimate utility functions via maximum likelihood logistic regression on American Community Survey data and solve for Nash equilibria at the block level. Results reveal that 93.5% of blocks are in transitional (off-equilibrium) states: approximately 31% exhibit walk-favored structural conditions but remain suppressed by coordination failures, representing high-leverage intervention targets, while 63% are transitioning toward automobile lock-in. Spatial analysis exposes stark environmental injustice—walkable hotspots cluster in the wealthy North Side and downtown, while car-dependent coldspots dominate the South and West sides. These findings establish that walking spreads as a social contagion through strategic complementarities, and that concentrated interventions achieving critical mass generate substantially higher returns than dispersed investments. The study provides a validated, spatially explicit framework for identifying tipping points and targeting active transport policies to maximize modal shift and advance environmental equity.