Spatiotemporal response of urban bike-sharing ridership to weather, air quality, and future climate change in major U.S. cities

Bike-sharing systems have become an essential component of sustainable urban transport, yet the resilience of system usage to changing environmental conditions remains insufficiently understood. This study provides a comprehensive spatiotemporal assessment of how weather and air quality influence bike-sharing ridership across five major U.S. cities between 2020 and 2024, and how these dynamics may evolve under future climate scenarios. Using generalized additive models, we reveal that primary weather variables mathematically dominate cycling decisions: ridership peaks around 20-25°C, while precipitation consistently suppresses usage. Conversely, air quality exerts a much weaker, secondary influence characterized by a behavioral dichotomy. Invisible, routine pollutants like ozone act as spurious proxies for pleasant weather, whereas physically perceptible hazards-such as acute wildfire smoke in San Francisco-can trigger sharp declines in usage. Hot spot analyses further show that environmental stress dynamically reconfigures spatial activity, driving a "climatic refuge" effect where cycling shifts toward waterfronts during extreme heat. Projecting these sensitivities forward, we show that future warming will enhance annual cycling suitability, particularly in seasonally cold cities, by reducing prohibitive winter days. Collectively, these results provide an integrated framework for understanding micromobility resilience, highlighting that urban cyclists respond primarily to immediate sensory environments rather than abstract health metrics.