Predictive modeling of children's thermal responses in urban under-bridge microclimates

As urban under-bridge spaces are increasingly utilized as shaded recreational zones, understanding the thermal responses of vulnerable users is important for developing safer and more responsive urban environments. However, current thermal comfort evaluation methods often assume a close correspondence between subjective thermal sensation and physiological response, which may not fully reflect the thermal characteristics of children in real outdoor environments. This study conducted a cross-seasonal field investigation in two representative under-bridge parks in Guangzhou, China, involving simultaneous measurements of environmental parameters, tympanic temperature (T_ty), and thermal sensation vote (TSV) for both children and adults. Regression-based predictive models were developed using environmental parameters and composite thermal comfort indices. The results showed that, under hot-humid summer conditions in shaded under-bridge spaces, both single environmental parameters and thermal comfort indices exhibited strong predictive capability for TSV, with R2 values generally ranging from 0.89 to 0.93. In addition, children tended to exhibit relatively higher tympanic temperatures at similar thermal sensation levels, suggesting a potential mismatch between subjective thermal sensation and physiological response. These findings may provide useful references for the thermal evaluation and environmental design of child-friendly urban microclimates.