Pedestrian Activity, Outdoor Thermal Comfort and Urban Street Design: Case Studies for the Seoul-Lo 7017 in Seoul and the High Line in New York City

Abstract

Designing thermally comfortable urban public spaces has become an important issue in urban design and planning. Due to rapid urbanization and climate change, the frequency and intensity of extreme heat events have sharply increased. This trend has led to multiple problems related to health and wellbeing of urban residents through multiple pathways. One of the key pathways is by negatively affecting pedestrian activities which are important forms of healthy outdoor physical and social activities. Specifically, the excess heat load causes significant pedestrian discomfort, which decreases the use of public spaces by altering the patterns of outdoor activities. To shape a safe and pleasant walking environment in the age of climate change, it is increasingly essential to understand the relationships between outdoor thermal comfort, pedestrian activities, and urban street design. Using the two urban walkway - ‘The High Line’ In New York City, U.S. and ‘Seoul-lo 7017’ in Seoul, South Korea - this dissertation research explored the relationship between thermal comfort and pedestrian activities (Topic 1) and its association with characteristics of urban street design (Topic 2). These walkways serve as ideal locations to explore this topic given primary function of leisure walking which responds more sensitively to the design and microclimatic characteristics of the streets than utilitarian walking. This research focuses on quantifying the impact of thermal comfort on pedestrian activity and the usage of street spaces, and on evaluating the association between thermal comfort and urban street design features. Given that the process of thermal adaptation shapes the heat-pedestrian activity relationship, this study further identified the heat thresholds of walking activity describing the range of tolerance of heat stress that respond to the different features of microclimate street design (Topic 3). The overall results of the three studies included in this dissertation research indicated that meteorological conditions and outdoor thermal comfort significantly impacted pedestrian activity. The first study showed that different meteorological (season, weather and microclimate) scales and components affected pedestrian activities differently. The second study indicated that the combination of urban design factors at the street- and block-scale levels influenced pedestrian thermal comfort. The last study suggested that a heat threshold of sitting and walking was influenced by sky view factors (SVFs) regulating solar access and shading effects. Findings from this study showed that proper modification of microclimatic street design features can improve pedestrian thermal comfort and increase the acceptable range of thermal conditions for walking and sitting activities. This study provides new empirical evidence to guide the design of highly heat-resistant street spaces that support pedestrian activities in the age of global warming.