A Study on Street Greenery Systems for Improving the Thermal Environment of Pedestrian Spaces†

This study proposes a practical framework for street greenery to improve the thermal environment in urban areas with high heat stress. Centering on sidewalk and road width as key planning variables, the framework systematizes criteria for multi-row tree planting, green-strip widths, and vegetated medians. Daegu Metropolitan City-one of South Korea’s hottest cities-served as the study area. Sixty-eight scenarios were designed and analyzed to develop and validate efficient application strategies for multi-row plantings and vegetated central medians to improve the urban thermal environment. Using the 3-D microclimate model ENVI-met 5.6.1, it was found that, irrespective of street orientation, two-row planting is effective at sidewalks≥6m wide, and three-row planting is effective at sidewalks≥10m wide. Roads with ≥4 lanes benefit from vegetated medians. Furthermore, based on a 2m effective sidewalk width, standards for the creation of street greenery strips were proposed, linking their width to the sidewalk width segments. The desirable standards were found to be; Under 3m (sidewalk width) → 1 row (of trees/shrubs) + under 1m (greenery strip width); 3m to under 4m → 1 row + 1m to under 2m; 4m to under 6m → 1 row + 2m; 6m to under 10m → 2 rows + 2m or more; 10m or more → 3 rows + 2m or more. Cooling is further enhanced when multi-row planting is combined with multi-layer vegetation (trees, sub-trees, shrubs). The integrated framework offers actionable guidance for rational planning and supports priority setting and strategic budget allocation for urban heat mitigation.