Phoenix evaluates reflective road coatings to mitigate urban heat

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In 2020, the City of Phoenix Street Transportation Department applied a light-colored, reflective coating called CoolSeal to 36 miles of residential roads and a public parking lot to combat the urban heat island effect. Researchers from Arizona State University studied the project and found that while the coating lowered road surface temperatures by up to 12°F, it increased mean radiant heat exposure for pedestrians by approximately 5.5°F during peak daylight hours. The findings highlighted a significant trade-off where reflective materials successfully cooled the asphalt but redirected heat toward people at street level.

Consequences

City officials are expected to integrate this research into the expansion of the Cool Corridors Program to determine which neighborhoods are best suited for reflective materials. Future planning will likely emphasize the necessity of combining road treatments with shade structures and tree canopy development, as reflective coatings alone are no longer viewed as a complete solution for urban heat mitigation.

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