Path-based Urban Shade Metrics: Integrating Pedestrian Thermal Comfort into Urban Design Guidelines

Urban shade is critical for mitigating pedestrian heat stress and improving thermal comfort, particularly in hot urban environments with intense solar radiation during summer. Traditional urban design practices often focus on overall shadow coverage ratios, which evaluate shading at the site scale rather than along specific pedestrian pathways. However, these approaches fail to adequately address the dynamic shading needs of pedestrians, whose thermal comfort is influenced by exposure patterns along their whole-trip. Based on the thermal comfort requirements of pedestrians during their trips, this study introduces two shade design control metrics: Pathway Shading Ratio and Maximum Allowable Continuous Sunlit Distance. Pathway Shading Ratio quantifies the proportion of shaded segments along a specified walking path, providing a baseline for the minimum shading quantity required across the entire route. Maximum Allowable Continuous Sunlit Distance defines an upper limit for the uninterrupted distance pedestrians can be exposed to direct sunlight, reflecting the temporal and spatial thresholds necessary to maintain acceptable thermal comfort during walking trips. By integrating field-based thermal comfort experiments with simulation analyses, this study systematically derives and quantifies these metrics. The findings establish a framework for targeted shading interventions, bridging the gap between urban shading design and pedestrian thermal comfort needs. This research refines urban shade evaluation systems, enhancing pedestrian thermal environments and providing actionable guidance for urban planners and policymakers to create thermally comfortable and walkable cities.