USA enters the era of new asphalt: the country is testing streets with reflective coating that reduces pavement heat, accumulates less temperature than traditional asphalt, and has already been applied to over 140 miles to combat urban heat islands.

Reflective coating applied on Phoenix streets transforms the pavement into part of the strategy against urban heat, with tests measuring thermal reduction, pedestrian limits, and maintenance challenges in a city marked by extreme temperatures.

Streets in Phoenix, United States, have started receiving a light and reflective coating to reduce pavement heating during periods of high sunlight, in a strategy that incorporates road infrastructure into tackling urban heat.

Called cool pavement, the technology is applied over existing asphalt and aims to decrease heat absorption in one of the hottest cities in the country, without requiring the complete replacement of already constructed streets.

The initiative gained scale after studies conducted by the Phoenix city government in partnership with Arizona State University, which evaluated the thermal performance of the material in residential neighborhoods and sections used for comparison.

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How reflective pavement works

Behind the so-called cool asphalt is a known physical principle: dark surfaces absorb more solar radiation, while light materials reflect a larger portion of light and tend to accumulate less thermal energy.

In common asphalt, heat concentrates throughout the day and is gradually released, keeping streets and neighborhoods warm even after the peak sun, especially in areas with little shade.

This behavior helps explain the phenomenon known as urban heat island, observed in regions where the concentration of impermeable surfaces alters how the city absorbs and returns heat to the environment.

Phoenix streets test reflective pavement that reduces asphalt heat and helps cities tackle urban heat islands.

In areas with many paved roads, parking lots, rigid facades, and little vegetation, the temperature tends to be higher than in regions with more shade, permeable soil, and vegetation cover.

In the case of Phoenix, the proposal does not involve tearing up the old pavement or rebuilding the entire road structure, but covering selected sections with a lighter and more reflective layer.

Applied over existing streets, the product allows the solution to be integrated into road maintenance programs, which reduces the complexity of the intervention when compared to complete reconstruction works.

The composition described in technical materials includes water, binders, mineral fillers, polymers, and components that help increase the surface’s reflectivity, maintaining compatibility with traditional asphalt pavements.

After the first tests started in 2020, the latest version, called by the city CoolSeal 2.0, was analyzed in a new phase to measure thermal performance and behavior over time.

Results Measured on Real Streets

The most highlighted data by the city hall is the surface temperature, an indicator used to measure how much heat the pavement absorbs during the day and how much it can return to the environment in the following hours.

In measurements released by the city, the coating reduced pavement heat by up to 12°F during the day, when compared to untreated aged asphalt streets.

In the first phase of the study, the average difference at noon and in the afternoon was between 10.5°F and 12°F, a range considered relevant for the comparison between treated and untreated surfaces.

Besides the visible layer, researchers recorded lower temperatures below the surface, a result that indicates less heat storage within the pavement structure in sections that received the coating.

This point is important because the street does not heat up only in the part exposed to the sun; part of the energy penetrates the material, remains accumulated, and influences thermal exchanges after the peak of insolation.

The experience began in residential neighborhoods and selected areas for comparison with untreated sections, allowing the city to evaluate the material’s performance in real everyday use conditions.

After the pilot, Phoenix incorporated the cool pavement into the permanent maintenance program of the Department of Street Transportation, expanding the application to dozens of neighborhoods in the city.

According to the city hall, more than 140 miles of roads have already received the coating, a milestone that placed Phoenix among the most observed municipal experiences in the use of reflective pavement on an urban scale.

This advancement draws attention because it occurs in a context of recurring extreme heat, where streets, parking lots, and other impermeable surfaces directly influence the thermal environment of neighborhoods.

Limits of Cool Asphalt in Urban Heat

Despite the results on the surface, the coating does not solve the problem of heat in cities on its own, as the temperature felt on the streets depends on a broader set of urban factors.

The evaluation released by the city hall itself indicates that the effects on air temperature still seem small, although they are considered beneficial within a combined climate adaptation strategy.

Between a less hot street and a more comfortable city, variables such as shade, wind, greenery, humidity, building height, traffic, street width, and materials used in the surroundings come into play.

Another relevant aspect involves the experience of those walking, because the greater reflection of light can alter the radiation perceived by pedestrians under certain conditions, especially when shade is lacking.

Studies on reflective pavements indicate that this exposure can increase at noon and in the afternoon in some scenarios, even though the surface presents a lower temperature in direct comparison with conventional asphalt.

For this reason, the solution tends to work better when combined with other urban adaptation measures, and not as a substitute for policies aimed at thermal comfort in public spaces.

Trees, adequate sidewalks, protected bus stops, reflective roofs, and shade corridors remain essential in regions subject to intense heat and long periods of solar exposure.

Within this set, cool pavement acts as an additional tool to reduce heat absorption in areas where asphalt occupies a large part of the urban landscape.

By reducing the thermal load accumulated on surfaces, the coating can contribute to a broader response to urban warming, provided it is applied with local planning and evaluation.

Durability of Street Coating

Streets of Phoenix test reflective pavement that reduces asphalt heat and helps cities tackle urban heat islands.

Large-scale application also depends on performance over time, as a layer used on streets needs to withstand wear from traffic, weather, and daily maintenance.

Tires, braking, dust, washing, repairs, repeated circulation, and intense temperature variations influence the lifespan of the coating, in addition to affecting the reflectivity observed in the first months.

According to the initial evaluation, the surface reflectivity decreased over the months, a behavior expected in materials exposed to continuous use and dirt accumulation on roads.

Even so, the treated sections remained more reflective than untreated conventional asphalt, which maintained part of the thermal benefit observed in the municipal program.

This monitoring is crucial to calculate cost, lifespan, and the need for reapplication, especially when the solution moves from the pilot phase to become part of routine road maintenance.

An urban technology only gains practical relevance when its results remain measurable after months or years of everyday use, under real traffic and varied weather conditions.

The debate also includes the type of road most suitable for the coating, as residential streets, parking lots, and low-speed areas have different demands from heavy traffic avenues.

In corridors with intense flow, wear, braking, and maintenance require specific evaluation, so that thermal reduction does not come with a loss of performance or incompatible costs.

Reflective pavement as climate infrastructure

Interest in reflective pavements is growing because many cities face a similar combination of factors, with dark, impermeable, and extensive surfaces acting as heat reservoirs.

In densely urbanized regions, replacing the entire urban form is expensive, complex, and time-consuming, while interventions on existing streets can fit into regular maintenance schedules.

Phoenix’s experience shows that the so-called cool asphalt is not a distant promise, but a solution already tested on real roads, with measurements made by the university and municipal public management.

In this approach, the innovation lies less in creating a completely new street and more in changing the interaction between the pavement and solar radiation throughout the day.

When the surface reflects more light and absorbs less heat, the road ceases to be just a passive element of the city and also fulfills a climatic function.

Even with this potential, the application needs to consider local climate, traffic intensity, pedestrian comfort, maintenance cost, and integration with shade and vegetation.

In hotter cities, the coating can be a useful piece, but it does not replace urban planning aimed at reducing heat nor other climate adaptation solutions.

USA enters the era of new asphalt: the country is testing streets with reflective coating that reduces pavement heat, accumulates less temperature than traditional asphalt, and has already been applied to over 140 miles to combat urban heat islands.