Transportation and sustainability officials in Phoenix and researchers Arizona State University have learned that that light-colored and reflective pavement can lower temperatures, effectively reducing the urban heat island effect. That could open the door for lower-cost, light-colored concrete pavements as a sustainable alternative to traditional pavement, writes Larry Scofield.



As one of U.S.’ hottest cities, it isn’t surprising that Phoenix is actively seeking ways to reduce air temperatures and improve the health and comfort of its residents. In Maricopa County, news outlets regularly report record-breaking heat. August 2020 was the hottest month on record since 1896 (when record-keeping began).

On June 17, 2021, a temperature of 118º F matched the hottest day recorded in any month during 2020. Furthermore, 323 heat-associated deaths were reported by Maricopa County in their final report for 2020 (the most recent year for which data is available). This figure represented a 62.3% increase from 2019 and was 15 times the amount from 2001.

In the context of the overall U.S., the CDC reported an average of 702 heat-related deaths annually during the time period from 2004 to 2018.

With Arizona suffering disproportionately, the contribution to the problem made by the 8,000 acres of regional freeway is coming under scrutiny. Paved surfaces absorb and store heat during the day and release it overnight, elevating ambient temperatures.

This phenomenon is known as the Urban Heat Island (UHI) effect. With paved surfaces comprising about 40% of the urban land area in Phoenix, they are often considered one of the primary causes of the UHI.

In response, the City of Phoenix Street Transportation Department and Office of Sustainability has been piloting a cool pavements program since 2020. The program is being conducted in partnership with Arizona State University (ASU).

In September 2021, year one results were presented by scientists from ASU’s Global Institute of Sustainability and Innovation, Healthy Urban Environments, and the Urban Climate Research Center. A key finding was that light-colored reflective pavement surface temperatures are considerably lower than those of traditional roadway pavement.