Impact of urban microclimate on walking volume by street type and heat-vulnerable age groups: Seoul's IoT sensor big data

There is an emerging interest in the association between walking and meteorological conditions. Despite the growing risk of heat stress, the city-wide evaluation of heat impact on walking at the street level has largely remained unknown. This study explores the association between ambient temperatures and the number of pedestrians in Seoul, considering the street's functional and user characteristics. Using big data on the urban microclimate and walking count obtained through urban internet of things sensor, heat–walking activity relationships were investigated between different settings of urban street types (commercial/shopping, outdoor marketplace, high-rise residential, and mixed-use) and the proportion of heat-vulnerable pedestrians (aged <9 or > 65 years) on a city-wide scale. Our study results indicated that the summer ambient temperature is crucial in determining walking count while showing nonlinear quadratic relationships. Its degree of impact is significantly associated with the day of the week and time of the day, with heat sensitivity of walking count being highest in mixed-use type streets. The negative impact of temperature increased as the proportion of heat-vulnerable age group of pedestrians increased in outdoor marketplace-type streets. Our findings highlight the significance of summer heat conditions on walking count while providing empirical evidence for establishing heat mitigation policies with enhanced street vitality.