Cool routes: Assessing how green space and paved paths modify heat's effects on urban bicycling.

BACKGROUND: Understanding how heat's effect on bicycling varies spatially across the urban environment can inform who may be bicycling in the heat and how urban-planning measures can improve thermal comfort for bicyclists. OBJECTIVE: We estimated effects of heat on recreational and commute bicycling in Denver, Colorado, USA using city-wide, finely resolved bicycling data and assessed heterogeneity in effects by area-level social vulnerability and proximity to the city center and whether off-street paths and green-space measures, if intervened upon, modify these effects. METHODS: From Strava Metro, we obtained daily data on recreational and commute bicycling in Denver on each street segment (N = 218,641) during the summer months of 2019-2023. We estimated effects of hot (95-99 °F [35-37 °C]) and very hot (100-104 °F [38-40 °C]) temperature on daily bicycling using model-based standardization, controlling for temporally varying confounders. We assessed effect heterogeneity by area-level social vulnerability and proximity to the city center. To assess effect modification by intervention (defined in text) of paved paths and green-space measures, we additionally controlled for social vulnerability and proximity to the urban core. RESULTS: Heat's attenuating effects on recreational and commute bicycling were stronger in central Denver but did not differ across area-level social vulnerability. Heat's attenuating effects were somewhat weaker on off-street paths and considerably weaker in greener areas and near blue space. CONCLUSIONS: Results support the provision of paved paths and access to green and blue space to support bicycling during hot weather.