Heat vulnerability and street-level outdoor thermal comfort in the city of Houston: Application of google street view image derived SVFs

Heatwaves and urban heat islands disproportionately affect residents of urban areas. Past studies on the heat vulnerability indexes (HVI) to evaluate the heat-related risk have two major limitations: the inability to capture street-level human heat stress and reliance on single meteorological proxies to measure heat exposure. To address these gaps, this study examines the impact of street-level outdoor thermal comfort (OTC) on heat vulnerability in the city of Houston, Texas. OTC refers to an individual's thermal perception of their surroundings. The study estimates the impacts of HVI scores and energy budget (EB) values of OTC on heat-related disease while investigating their spatial distributions and clusters. The results show that the explanatory power of the suggested models on the number of emergency department (ED) visits improved when the street-level OTC had higher HVI scores and more comfortable conditions. A positive bivariate relationship was found between the HVI scores and EB values, showing the highest explanatory power (adj-r2) of around 36%. Chronic disease and heat exposure significantly affected the HVI, whereas tree and sky view factors were crucial determinants of the EB values. These findings provide a new approach to heat vulnerability evaluation at the human scale to effectively address heat-related risk.