Phoenix swapped black asphalt for a reflective road coating; noon surface heat fell 12°F, but pedestrians faced higher radiant heat
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Business News›News›International›US News›Phoenix swapped black asphalt for a reflective road coating; noon surface heat fell 12°F, but pedestrians faced higher radiant heat
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Phoenix swapped black asphalt for a reflective road coating; noon surface heat fell 12°F, but pedestrians faced higher radiant heat
SECTIONS<br>Phoenix swapped black asphalt for a reflective road coating; noon surface heat fell 12°F, but pedestrians faced higher radiant heat
By Team Global
, Global DeskLast Updated: Aug 23, 2026, 01:10:00 PM IST<br>Rate Story
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Synopsis<br>In an effort to lower urban heat, Phoenix tested innovative reflective pavement coatings on its roads, revealing that treated asphalt kept cooler than traditional options. Despite this advantage, the reflective nature led to intensified heat for pedestrians in the vicinity. Further complicating matters, the effectiveness of these coatings decreased with time due to dirt and degradation, driving cities to consider these factors for enhanced comfort levels for their residents.
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Same street, two surfaces: Phoenix tested a reflective coating against regular asphalt (representative image). Image Credits: ChatGPT
Phoenix is one of the hottest cities in the United States, so in 2020 the city tried a new way to cool things down. Rather than plain black asphalt, the city painted some roads with a light-colored, reflective coating, on the theory that a lighter road would keep cooler. A year-long study was performed by Arizona State University (ASU) to test this, and the Cool Pavement Pilot Program report summarizes the results.
What Phoenix actually did
The City of Phoenix Street Transportation Department teamed up with ASU’s Urban Climate Research Center. In the period between July 15, 2020 and July 14, 2021, they used the coating for roads in various neighborhoods and then compared them with uncoated asphalt in the surrounding areas. At the surface level, the coating did its job. The ASU report says treated roads were 2.4 degrees Fahrenheit cooler at sunrise, 12 degrees cooler at noon, and 10.5 degrees cooler in the afternoon compared to conventional, aged asphalt. Even the ground beneath the surface was an average of 4.8°F cooler, which matters in a city where roads can get hot enough to burn skin.
The catch nobody expected
A cooler road doesn’t necessarily mean a cooler walk. The reflective coating reflects more sunlight than it absorbs, which helps keep the surface cooler. However, the reflected rays are then directed back at the pedestrians walking close to the surface. The research found that mean radiant temperature, a measure of the thermal radiation absorbed by the body outdoors, rose by an average of 5.5°F on the coated streets. The finding is consistent with other research. In a separate study titled ‘Solar reflective pavements: A policy panacea to heat mitigation?’ published in Environmental Research Letters, ASU researcher Ariane Middel and colleagues tested a similar coating in two Los Angeles neighborhoods. It noted surface temperatures dropped 4°F to 6°F, but mean radiant temperature over the pavement rose about 4°C (7.2°F) at midday, while air temperature fell only slightly.
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Why a cooler road doesn't always mean a cooler walk: reflected sunlight has to land somewhere (representative image). Image Credits: ChatGPT
The coating also wears off over time. It was brightest just after it was applied and reflected about 33 to 38 percent of sun radiation, but after ten months of exposure, this figure was down to 19 to 30 percent, due to accumulated dirt and general wear. A typical asphalt surface reflects about 12 percent of sunlight. Even a faded coating is better than plain asphalt, but the margin is smaller.
A longer-lasting second version, and a bigger-picture study
Based on these results, Phoenix and ASU tested a new version of the pavement coating in seven additional neighborhoods from May 31 to June 6, 2022, and released their findings in October 2024. Cool pavement technology, according to this phase of the...