The City of Phoenix, AZ has released the results of the first year of its Cool Pavement Pilot Program. In 2020, the city selected areas in eight neighborhoods to receive the cool pavement treatment. Cool pavement is a water-based asphalt treatment that is applied on top of the existing asphalt pavement. As the treatment reflects back the sunlight that hits it – rather than retaining the heat – it has the potential to offset rising nighttime temperatures. It’s hoped that the use of cool pavement technology will help reduce the heat island effect and reduce temperatures in the city. The project is run by the City of Phoenix Street Transportation Department and Office of Sustainability in partnership with Arizona State University (ASU).
Researchers at ASU’s Global Institute of Sustainability and Innovation, Healthy Urban Environments, and the Urban Climate Research Center concluded that the reflective pavement surface temperatures are considerably lower than traditional asphalt. Overall, surface solar reflectivity decreased over 10 months from a range of 33-38% to 19-30%.
The data was collected in a number of ways: thermal imaging by helicopter flyovers; temperature sensors embedded in the pavement surface; a vehicle equipped with air and surface temperature sensors that traveled over the treated areas to gather data; and MaRTy (derived from ‘Mean Radiant Temperature’) – a specially designed mobile weather station that evaluates the human experience of heat.
“This is exactly what we were hoping for,” Phoenix Mayor Kate Gallego said. “While there’s more work to be done, it’s exciting to see a technology that has the potential to meet the demands of a growing desert city in a world where temperatures are constantly climbing.”