Modeling extreme heat at transit stops and its implications for equity

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The combination of urban population growth, global climate change and urban heat island effect has increased the number of individuals exposed to extreme heat and the frequency of extreme heat events, including in cities that previously had little exposure to such events. Extreme heat tends to have the biggest impact on less-resourced and socio-economically vulnerable populations so studying the impacts of urban heat and strategies to avoid them comprise a critical pillar to ensuring urban climate equity and resilience. While extreme heat events impact individuals from all socio-economic backgrounds, risks associated with public transit ridership particularly affect lower-income households. This project investigates the extreme heat conditions commuters are faced with, how environmental conditions affect heat exposure, perceptions of extreme heat risk, and how heat exposure might ultimately affect usage of transit systems. Transit stops are arrayed across a pre-existing landscape of roadways, buildings, vegetation, and socio-economic conditions and their thermal environments are influenced by patterns at multiple scales. At coarser spatial scales the built environment and vegetation interact to drive microclimates that can be many city blocks in size. But fine-scale conditions including shade structures, tree canopy and proximal built infrastructure result in significant temperature differentials as well. Transit users’ thermal experience is determined at both scales when waiting at a stop or when traversing other public spaces to arrive at a transit stop. The more dependent a person is on transit the longer they will face climate exposures in these environments. As a result, thermal exposures at transit stops are an issue of environmental justice, particularly if there is an inequitable distribution of urban heat with respect to socio-economic status, race, and other factors. This project addresses these issues by investigating 1) how urban planning and economic dynamics drive urban form and land cover composition; 2) how urban form and land cover affect outdoor mean radiant temperature and measured thermal comfort at transit stops; 3) how heat exposure at transit stops drives perceptions of thermal comfort by riders and 4) how microclimate and perceived thermal comfort influence transit ridership behaviors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.