Phoenix's reflective road coating cut surface heat by 12°F but raised radiant heat for pedestrians

Phoenix tried a reflective coating on black asphalt; noon surface heat fell 12°F

In 2020, Phoenix partnered with Arizona State University to test a reflective coating on some roads, aiming to reduce urban heat. A year-long study showed treated surfaces were up to 12°F cooler at noon, but the coating also reflected more sunlight back at pedestrians, raising mean radiant temperature by 5.5°F. The coating's reflectivity faded over time, and a follow-up review found it works best in open, low-traffic areas, not where people gather. Cities like San Antonio are also experimenting, but experts remain cautious.