Los Angeles Is Painting Its Streets To Fight Heat Waves

Researchers found that coating more than 700,000 square feet of asphalt in a Los Angeles neighborhood with a solar-reflective material helped reduce urban heat, though the benefits came with limitations, according to the Times of India.

The project, conducted in Pacoima in the San Fernando Valley and published in Environmental Research Communications, covered roads, parking lots, playgrounds, and basketball courts with a reflective coating designed to bounce sunlight away instead of absorbing it. During a September 2022 heat wave, afternoon air temperatures in treated areas were as much as 3.5°F (1.9°C) cooler than in a nearby untreated neighborhood. Pavement surface temperatures also dropped by roughly 10°F.

The report says that researchers cautioned, however, that cooler pavement doesn't always translate into greater comfort for pedestrians. While reflective surfaces absorb less heat, they can also reflect more solar radiation back into the surrounding environment, potentially increasing the radiant heat people experience. Factors such as direct sunlight, humidity, wind, and surrounding surfaces all influence how hot it actually feels outdoors.

The findings suggest reflective pavement can help reduce urban heat, particularly during extreme heat waves, but works best as part of a broader strategy that also includes trees, shade, and other cooling measures. Researchers also noted that coatings can lose effectiveness over time due to weather, traffic, dirt, and routine road maintenance.