Highways·Phoenix Cool Pavement Programme·—·Phoenix Cool Pavement Programme

Phoenix Cool Pavement Programme

100+ miles treated · 6°C surface temp reduction · $4.8m annual

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Key insight

Cool pavement also extends road longevity by reducing thermal degradation — delivering avoided maintenance costs beyond the cooling benefit. Funded from existing pavement maintenance budgets, not additional climate spend.

Transferability to UK: MediumDirectly applicable to UK cities experiencing urban heat island intensification.

Reflective CoolSeal coating applied to 100+ miles of residential roads to combat extreme urban heat island effect. The product increases road reflectivity by 30% and reduces surface temperatures by 6°C, integrated into existing pavement maintenance budgets.

Climate drivers

High temperaturesUrban Heat Island effect

Impacts

→Road surface overheating→Increased energy demand

Adaptation measures

  • CoolSeal reflective coating
  • Pavement maintenance programme
  • University monitoring partnership

Assets affected

Road pavement

Investment

USD $4.8m annual (£3.73m); initial pilot £2.33m

Band: £1m–£10m

Delivery period

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  • Phoenix, Arizona is the hottest city in the United States .
  • In July 2024, daily average temperatures rose to a record peak of 47.8 ° C. This formed part of a record 81 days above 37.8 ° C, including 16 consecutive nights above 32 ° C .
  • During this period, 466 heat-related deaths were confirmed in Maricopa County, Arizona’s biggest metropolitan area, with a further 191 under investigation . The heatwave was accompanied by high humidity, which reduces the body’s ability to regulate heat, leading to heat-related illness.
  • Global temperature increases disproportionately affect cities because of the urban heat island (UHI) effect, where cities retain heat during nights more than rural areas.
  • UHI is caused by factors such as the use of building materials, which can absorb and retain heat to a greater degree than natural environments .
  • Asphalt contributes to UHI due to its dark colour and is primarily used in road and pavement .
  • Road surfaces represent 30-40% of Phoenix’s metropolitan area and cover 5,000 miles of land .
  • Black asphalt has a low albedo (surface reflectivity) of just 0.03-0.04, with a high thermal mass and storage capacity for heat. Consequently, asphalt pavements absorb heat during the day making the surrounding areas hotter by elevating both daytime and overnight surface temperatures through the release of this heat . This increases UHI effects.
  • Higher temperatures contribute to increased energy consumption and GHG emissions in cities .

Ref: ID_19 · Phoenix Cool Pavement Programme · Curated & verified by HIVE

Transferability to UK: Medium

Directly applicable to UK cities experiencing urban heat island intensification. London hotspots already 4.5°C warmer at night than rural surroundings. Heat-related deaths in London more than doubled in 2022. Currently limited to streets with ≤25mph speed limit due to skid resistance constraints.

UK contexts

London urban roadsMajor UK city centresTransport for London managed streetsLocal authority highway maintenance programmes

Applicable to UK urban areas

Transfer to other sectors (AI)