Thermal Comfort Assessment of Multimodal Corridors in Tucson, Arizona, to Increase Heat Resilience

Thermal comfort assessment of multi-modal corridors in Tucson, Arizona to increase heat resilience

Zeinab (Ida) Sami¹, and Ladd Keith, Ph.D.²

¹Arid Lands Resource Sciences, University of Arizona, Tucson, AZ 85721

² School of Landscape Architecture and Planning, University of Arizona, Tucson, AZ 85721

Cities are a lot warmer than nearby rural areas (Filho et al. 2018). This phenomenon, known as urban heat island (UHI) effect, results from the energy created by urban structures, human activities, cars, etc. (Oke, 1973). In addition, buildings, roads, and other subsurface materials absorb solar radiation during the daytime, and reradiate to the surrounding environment, causing temperature elevation in cities (Du et al., 2008). Extreme heat, through contributors such as the UHI effect and rising temperatures due to climate change are increasing heat stress of pedestrians (Arnfield, 2003). This increased heat stress may affect the use of public spaces and influence human mobility patterns (Van Hove, 2015). The multi-model urban corridor, a parallel transportation facility for moving people and goods between two points (Dowling et al., 2002), is one of the impacting factors for researching heat stress effect on pedestrian thermal comfort. Thermal comfort is “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation” (ANSI/ASHRAE Standard 55, 2004). Ensuring multi-model corridors are comfortable for pedestrians contributes to the city’s ability to attract and encourage people to spend more time in the outside, and consequently will benefit the city from various perspectives, including physical, environmental, economic, and social aspects (Hakim et al., 1998; Fuller and Moore, 2017). The multi-model corridors aim to create social and economic linkage between important zones of the city. However, many cities in hot and arid climates are warming fastest due to both UHI and climate change. Urban planners lack suitable design tools to plan effectively for corridors in a hot climate (Johansson and Emmanuel, 2008), further complicated by heat as a climate risk being specifically addressed in only 4% of climate adaptation resources (Nordgren et al., 2016). Increasing the awareness of climate considerations among urban planners is essential; to design corridors that improve thermal comfort for pedestrians.

The City of Tucson, located in the Sonoran Desert with a hot desert climate (Beck et al., 2018), is the 3rd fastest-warming city in the United States with a 4.48°F (2.49°C) rise in temperature between 1970 and 2018 (“American Warming”, 2019). That warming is at the root of serious threats to vulnerable individuals such as elderly people, infants, and those with physical impairments or those who can’t afford mitigation measures (Patz et al. 2005). Therefore, it is essential to understand thermal comfort at the pedestrian level and, through a better understanding of the corridor typologies, propose design interventions to mitigate heat stress.

This research aims to study the thermal comfort of pedestrians in several multi-modal corridors within the City of Tucson to document ambient and radiant temperatures of different multi-modal corridor typologies and to understand the effect of heat stress on pedestrian mobility patterns. Corridors will be selected based on interviews with local urban planners, considering locations vulnerable populations, corridor typology, and pedestrian usage. Methods proposed for this study include pedestrian surveys on thermal comfort, field measurements of ambient and radiant air temperatures, and corridor-use observations. In addition, a quantitative method will be used in this study by calculating the Universal Thermal Comfort Index (UTCI) in various locations to measure existing thermal comfort level at the selected corridors. Results from this study will directly connect to urban planning practices by informing planners about effective strategies in designing multi-model corridors with a high thermal comfort level.

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