In 2020, Phoenix coated 36 miles of roads to fight extreme heat; surfaces became 12°F cooler at noon

Phoenix coated 36 miles of roads to fight extreme heat 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. The roads also store heat and slowly release it after sunset, keeping urban areas warm through the night. To reduce this effect, Phoenix applied a reflective coating to selected residential streets across eight council districts. ASU researchers found that...