Cross-Climatic Assessment of Thermal-Comfort Vitality in Commercial Pedestrian Streets

Rapid urbanisation and climate change are intensifying pedestrian-level heat stress in cities. Although outdoor thermal comfort has been widely studied, existing research remains fragmented: most studies address single climates or air temperature alone, and few translate physical thermal conditions into indicators of pedestrian behaviour or provide a standardised cross-climatic comparison of commercial pedestrian streets. As a result, there is no transferable way to express how the thermal environment shapes the usability of such streets across climates. This study develops and tests a behavioural framework linking outdoor thermal comfort to street usability in commercial pedestrian streets across contrasting Köppen climate zones. Its core is the PET → POP → UCH chain, which converts thermal comfort (PET) into pedestrian occupancy potential (POP) and aggregates it into Usable Commercial Hours (UCH), a temporally integrated measure of the thermal-comfort dimension of street vitality. The POP formulation embeds an a priori, literature-derived threshold.It is tested in two field cities under an identical protocol: Darwin (Aw), the pilot, and Shanghai (Cfa), an independent replication, each combining unobtrusive pedestrian observation, on-site microclimate measurement, and a field-validated ENVI-met model (evaluated by r², RMSE, MBE). Panel fixed-effects regression tests whether thermal comfort affects staying behaviour, and segmented regression tests this threshold against observed behaviour. Agreement across the two climates licenses transfer of the validated model, by simulation, to Singapore (Af) and Harbin (Dwa), enabling a cross-climatic comparison of UCH on matched streets. Two derived applications follow: future-climate projection of UCH under SSP2-4.5 and SSP5-8.5 (2050, 2080) using CMIP6-based weather files via epwshiftr, and cross-climatic mitigation analysis expressed as change in usable hours (ΔUCH). The overarching contribution is a validated, transferable framework connecting street-scale microclimate to pedestrian staying behaviour, with the UCH metric and its cross-climatic design implications as the central innovation.