Evaluating the impacts of cool pavement on pedestrian-level heat stress indicators

Extreme heat is an increasing hazard in communities across the world due to climate change and urbanization patterns resulting in urban heat. Transportation infrastructure, such as road pavement, is a well-known contributor to the urban heat island effect. Engineered pavement coatings, known as cool pavement, reflect light and heat to reduce the thermal load of roads and reduce urban heat, but their effect on heat stress, and therefore human thermal comfort, of travelers such as pedestrians, cyclists, and transit riders, is still an underexplored area. The City of Tucson, Arizona, applied a cool pavement pilot of the PlusTi asphalt rejuvenator in 2021 as a part of its Parks and Connections Bond. Previous studies on cool pavement asphalt rejuvenators have found inconsistencies in the magnitude of their cooling properties in the lab versus real-world settings. We conducted a before-after natural study design to evaluate the impacts of the cool pavement application on indicators of heat stress, including ambient air temperature (TA) and wet bulb globe temperature (WBGT). Once temporal autocorrelation is accounted for, we found that the PlusTi asphalt rejuvenator resulted in 0.11 °C (0.2 °F) more TA observed and no statistical difference in WBGT, indicating minimal negative impacts to heat stress indicators in this natural experiment setting. Continued evaluation of cool pavement products is critical to better understand their potential in mitigating urban heat and ensuring minimal negative impacts on heat stress indicators.