Thermal comfort and physiological responses to summer street microclimate variations: a case study of Nanjing East Road, Shanghai

Outdoor thermal comfort studies rarely integrate physiological responses with subjective perception, leaving a gap in dynamic street environments. Most rely on indoor steady-state standards or questionnaires alone. This study addresses this gap by conducting summer field measurements on Nanjing East Road, Shanghai, using wearable sensors to capture seven physiological indicators alongside microclimate data and thermal comfort votes at 12 points under four top shading types. Quantitative results show that all seven physiological indicators correlate significantly with thermal sensation vote and thermal comfort vote (finger skin temperature highest). Heart rate, heart rate variability, chest skin temperature, and blood oxygen saturation responded primarily to short term thermal fluctuations, whereas finger skin temperature and skin conductance level exhibited gradual increases over time. However, indoor steady-state standards are inapplicable: outdoor comfort occurs at higher mean heart rate (>75 bpm) and lower heart rate variability (<1.5 – 2.0) than indoor norms, and chest skin temperature deviates from 32°C. Shading degree improves physiological comfort more than shading material type, and higher top shading consistently enhances comfort regardless of building or tree shade. This study provides a replicable physiological based methodology for evaluating street thermal comfort, and offers design guidance for construction of comfortable urban street.