Want Cooler Cities? Doing This One Thing to Roads Can Help With That - ScienceAlert

When heat waves hit, people start looking for anything that might lower the temperature.

Research shows that building lighter-colored, more reflective roads has the potential to lower air temperatures by more than 2.5 degrees Fahrenheit (1.4 C) and, in the process, reduce the frequency of heat waves by 41 percent across U.S.

But reflective surfaces have to be used strategically – the wrong placement can actually heat up nearby buildings instead of cooling things down.

In urban areas, about 40 percent of the land is paved, and that pavement absorbs solar radiation.

This can exacerbate urban heat islands and worsen the effects of heat waves.

The lower a surface's albedo, the more light it absorbs and, consequentially, the more heat it traps.

Conventional pavements such as asphalt have a low albedo of around 0.05-0.1, meaning they reflect only 5 percent to 10 percent of the light they receive and absorb as much as 95 percent.

When pavements instead use brighter additives, reflective aggregates, light-reflective surface coatings, or lighter paving materials like concrete, they can triple the albedo, sending more radiation back into space.

In a few low, sparse downtown neighborhoods, we found that reflective pavement could raise the demand for cooling because of increased incident radiation on the buildings.