Phoenix cool pavement cut road heat by 12F but raised pedestrian heat exposure
A study in Phoenix found that reflective 'cool pavement' coatings successfully lower road surface temperatures but increase heat exposure for pedestrians. The reflective material bounces sunlight toward people walking on the street, creating a trade-off between infrastructure cooling and human comfort.
Why it matters
The findings challenge urban planning assumptions about heat mitigation and highlight the need for human-centric design in climate adaptation strategies.
Painting city streets with a light-coloured, reflective coating can cool the asphalt underneath, but it can also increase heat exposure for people walking on the road. That unexpected trade-off emerged from a major trial in the American Southwest. In 2020, the City of Phoenix Street Transportation Department coated 36 miles of neighbourhood roads and a public parking lot with CoolSeal, a grey, water-based asphalt treatment designed to reduce the urban heat island effect. Researchers from Arizona State University (ASU) studied the treated roads for a year. Their findings showed that while the coating successfully lowered road temperatures, it also created a more complicated situation for pedestrian comfort and safety.Why the roads became coolerTraditional dark asphalt absorbs large amounts of sunlight and can reach temperatures of up to 180°F during the hottest summer periods.
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