Investigating the potential of street trees in mitigating pedestrian thermal stress during heatwaves conditions: An empirical study in Guangzhou

Given the escalating urban heat island phenomenon and increasing frequency of heatwaves across the globe, many recent studies have focused on protecting human health from outdoor heat stress. Public commuting was the primary transportation way. However, there has been a significant oversight regarding the specific issue of heat stress encountered by commuters, particularly pedestrians on sidewalks lacking sufficient shade. This research gap leaves certain urban residents highly vulnerable to the negative effects of heatwaves. To address this issue, the thermal walking method was employed in this study to evaluate the physical thermal stress and thermal perceptions of Guangzhou residents during their commutes. Additionally, this study developed a regression model to evaluate the heat tolerance of street trees and their impact on pedestrians' experiences. The findings indicate that street trees substantially influence key thermal environment indicators, particularly solar radiation and surface temperature. These trees also play a pivotal role in shaping pedestrians' perceptions of thermal sensations by affecting the intensity, sequence, and duration of their exposure to heat. Significant variations were found in pedestrians' experiences under different street trees, mainly due to the trees’ rebound effects. Pedestrians exhibit a higher heat tolerance when the ΔUTCI of this rebound effect surpasses 6 °C (TCV >1 and TAV ≥ −0.01), indicating a generally favourable response to the prevailing outdoor thermal conditions. This research offers valuable insights into the cooling effects of street trees, which may help city planners improve urban living standards through feasible, nature-oriented strategies. •The UTCI has limitations in predicting pedestrian thermal perception during heatwaves.•Street tree shadows' rebound effects modify pedestrians' thermal perceptions.•Pedestrians' sunlight exposure shouldn't exceed 10 min at a time during heatwaves.•Pedestrians' thermal tolerance requires a rebound effect greater than 6 °C.