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Street Paint Cools Roads, Hotter for Pedestrians
23 Aug
Summary
- Reflective street coating lowers road temperature significantly.
- Pedestrians face increased heat radiation exposure.
- Shade and greenery are vital for true heat solutions.
In a significant urban heat island mitigation effort, Phoenix, Arizona, applied a light-coloured, reflective coating to 36 miles of neighbourhood roads and a parking lot in 2020. This treatment, designed to reduce asphalt temperatures, was studied by Arizona State University researchers for a year.
The findings revealed that the coated roads were cooler by 2.4°F at sunrise and 10.5 to 12°F cooler around midday compared to traditional dark asphalt. This also extended to subsurface temperatures, potentially increasing road longevity.
However, the study uncovered an unexpected consequence: increased heat exposure for pedestrians. Reflected solar energy was redirected, raising the mean radiant temperature around coated streets by approximately 5.5°F during peak heat. This highlights a complex trade-off in cooling strategies.
Urban planners are taking note of these Phoenix results, as cities globally seek solutions for rising temperatures. Experts stress that reflective coatings are not a panacea. They advocate for integrated approaches that include shade from trees and buildings to ensure comprehensive heat mitigation and pedestrian comfort.
