Research Team | PI: Ladd Keith; Co-I: Nicole Iroz-Elardo and Kristi Currans; Graduate Students: Lauren Heath and Ethan Wissler; Undergraduate Students: Ashley Avilla and Brenden James Little
Funding | U.S. Department of Transportation, National Institute for Transportation & Communities (NITC)
Description | Road pavement is a known contributor to the urban heat island effect. Several vendors are providing engineered pavements coatings – known as “cool pavement” – to reflect light and therefore heat to reduce the thermal load of roads. The City of Tucson is planning a pilot application of a cool pavement in Fall 2021 as a part of its Parks and Connections Bond work; our team has been working with the city and vendor(s) to set up an evaluation framework of the cool pavement.
Few of these cool pavements have been evaluated outside lab conditions, particularly in the desert southwest. Lab testing tends to rely heavily on surface temperature measurements with the assumption that lower surface temperatures result in the pavement being less of a heat sink and thus lowers ambient temperatures in real-world practice. Further, while heat is detrimental to the pedestrian and cyclist experience and health, almost no research exists documenting the experience of the cool pavement on active travelers including their perception of heat.
We propose a pre/post, case/control quasi-experimental design to evaluate the impacts of the cool pavement on the following heat metrics:
• Surface temperatures of the pavement
• Ambient temperatures of the area
• Thermal comfort as measured by wet bulb globe temperature (WBGT)
Governmental occupational guidance for exertion for heat is based on studies in industrial settings using wet-bulb globe temperature (WBGT), a heat index that incorporates ambient air temperature, humidity, airflow, and radiant solar heat. Known as “thermal comfort”, this index better mirrors the human – and thus pedestrian and cyclist – experience.
We anticipate four 12-hour days in the field. Each day will include seven Kestrel 5400 stations for ambient and WBGT temperatures at least every minute and surface temperatures every hour. Data will be managed and analyzed in R; outputs will include basic summary statistics, graphics, and regression analysis.
Our team has steadily increased capacity for such research over the past 2 years. In summer of 2019, Iroz-Elardo and Keith piloted a methodology to investigate how shade structures and surface materials in school gardens and play structures influenced thermal comfort as measured with a WBGT instrument and thermal heat guns. In late-spring 2020, Keith and Iroz-Elardo applied this knowledge to evaluate heat risk at COVID-19 vaccine point of distribution (POD) drive-in centers in Tucson. One of the more interesting preliminary findings from the vaccine POD evaluation was the extent to which idling vehicles appear to raise the WBGT in outdoor settings due to both mechanical and radiant heat.
- NITC Awards $485,456 in Funding for Seven New Research Projects, National Institute for Transportation & Communities (NITC), August 17, 2021.
- City of Tucson Cool Pavement information page
- CAPLA Urban Planning Professors Awarded $150,000 in NITC Research Grants, The University of Arizona College of Architecture, Planning, and Landscape Architecture, August 27, 2021.
- Kennedy, Sarah. “Titanium dioxide coating could keep roads and bike paths cooler.” Yale Climate Connections. October 18, 2022.
- Aratani, Lori. “As temperatures rise, this research could help cities stay cool.” Washington Post. July 8, 2022.
- Giuliano, Tina. “City of Tucson’s Cool Pavement project expected to cool down roadways.” KGUN9. January 26, 2022.
- Currier, Carsyn. “Cool Pavement Project could lead to less carbon emissions, cooler roadway temperatures.” KOLD News 13. January 12, 2022.
- Costantino, Nicole. “UArizona “cool pavement” program aims to beat Tucson’s extreme heat.” KVOA. December 15, 2021.