Modeling extreme heat at transit stops and its implications for equity

城市人口增长、全球气候变化和城市热岛效应加在一起，增加了暴露在极端高温下的人数和极端高温事件的频率，包括在以前很少暴露在这种事件下的城市。极端高温往往对资源较少和社会经济脆弱的人群产生最大的影响，因此研究城市高温的影响和避免这些影响的战略是确保城市气候公平和复原力的关键支柱。虽然极端高温事件会影响所有社会经济背景的个人，但与公共交通乘客相关的风险尤其会影响低收入家庭。该项目调查了通勤者面临的极端高温条件，环境条件如何影响热暴露，对极端高温风险的看法，以及热暴露最终如何影响交通系统的使用。公交车站排列在预先存在的道路，建筑物，植被和社会经济条件的景观，其热环境受到多尺度模式的影响。在较粗的空间尺度上，建筑环境和植被相互作用，形成了许多城市街区大小的小气候。但是，包括树荫结构、树冠和邻近建筑基础设施在内的精细尺度条件也会导致显著的温差。公交用户的热体验是在两个尺度上确定的，当在车站等待或穿过其他公共空间到达公交车站时。一个人越依赖过境，他们在这些环境中面临气候暴露的时间就越长。因此，公交站点的热暴露是一个环境正义问题，特别是如果城市热量在社会经济地位、种族和其他因素方面分布不公平的话。该项目通过调查1）城市规划和经济动态如何驱动城市形态和土地覆盖组成来解决这些问题; 2）城市形态和土地覆盖如何影响室外平均辐射温度和在公交站点测量的热舒适度; 3）公交站点的热暴露如何推动乘客对热舒适度的感知; 4）该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.