ASU and City of Phoenix Officials Reveal Results of Second Phase of Cool Pavement Scientific Testing

Yearlong research demonstrates cool pavement continues to effectively reduce summer surface temperatures up to 12°F compared to conventional aged pavement during the day.

​The City of Phoenix Street Transportation Department partnered with the Rob and Melani Walton Sustainability Solutions Service at Arizona State University to evaluate the effectiveness, performance, and potential co-benefits of the new CoolSeal 2.0 pavement coating, a continuation of the City's Cool Pavement Program. Last week, the City of Phoenix joined ASU researchers at Burton Barr Central Library to present the results of the most recent research phase.

Some of the key research findings include:

• Cool pavement effectively reduces summer surface temperatures, up to 12°F, compared to conventional aged pavement during the day.
• Cool pavement may ultimately reduce long-term road maintenance needs and costs, which could yield substantive economic and environmental benefits.
  
• Cool pavement impacts on air temperature thus far appear to be small but beneficial.

"Phoenix is a city leader in cool pavement implementation, testing, and driving industry innovation," said Jenni Vanos, Associate Professor at ASU and member of the research team that conducted the study. "While continued testing will be crucial in the long-term, there is no way to know how this works in the real world unless you test it in the real world, and we've started that important effort here in Phoenix."

An executive summary of the report's findings is available at Phoenix.gov/Streets/CoolPavement.

"This unique partnership with ASU continues to guide the Street Transportation Department in our cool pavement application planning and strategy. We are grateful to ASU for the work that has been put into this yearlong study," said Brandy Kelso, Interim Director for City of Phoenix Street Transportation Department.

The City-ASU partnership continued into Phase II in 2022, building upon findings from Phase I in 2021. In the summer of 2022, researchers continued investigating the thermal performance of the cool pavement surfaces in residential areas. Products tested included the new "Phoenix Gray," or CoolSeal 2.0, created by CoolSeal by GuardTop® in response to Phoenix residents asking for a darker color and different formulations.

"The lifespan of the cool pavement seal coat is approximately eight years, as opposed to four years, for a traditional black seal coat," said Ryan Stevens, a Professional Engineer with the Phoenix Street Transportation Department. "Since the cool pavement seal coat reduces the temperature of the asphalt underneath the surface, this will lead to a longer lifespan for the road, increasing the service life before the next major maintenance activity, like a mill and overlay."

To learn more about cool pavement in Phoenix or view the results of the second year of scientific testing, visit Phoenix.gov/Streets/CoolPavement.

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