Street greenery design strategies to mitigate urban heat islands using the 2D and 3D streetscape indices

Streetscapes consist of diverse spatial components from both 2D and 3D perspectives, which influence the urban thermal environment. In particular, the spatial composition of streets — including vegetation, buildings, roads, and open sky — plays a significant role in altering apparent temperature, a key indicator of thermal comfort. Therefore, this study proposes street greenery design strategies for mitigating urban heat islands by integrating both 2D and 3D streetscape indices based on spatial characteristics of streets. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) were extracted from satellite imagery and utilized as 2D indices. In addition, Google Street View (GSV) images were processed through semantic segmentation to derive 3D indices, including green view index (GVI), building view index (BVI), road view index (RVI), and sky view index (SVI). The AT was employed to assess the thermal environment. The correlation value between NDVI and AT showed relatively high across the study area, indicating that the 2D vegetation distribution plays a significant role in cooling the street environment. However, the analysis also highlighted that the effect of streetscape elements on AT varied depending on the spatial characteristics and surrounding conditions of each street. This study suggests that street greenery design should be tailored to the specific context of streetscapes, considering both 2D and 3D spatial structures to maximize the cooling effect. The findings provide practical implications for urban planning and landscape design to enhance thermal comfort in rapidly warming cities.