Thanks in part to heat-absorbing materials and colors, cities tend to be warmer than their natural surroundings, and in hot places with lots of dark roads like Los Angeles that can prove a serious public health hazard.The mayor has pledged to reduce temperatures in the city by 3 degrees over the next 20 years, in part by dealing with urban heat island effects in new and different ways.

As part of this promise to help make bring down temperatures for its millions of residents, LA is trying something that could dramatically change its urban landscape: repainting roads in white. The aim is to reflect rather than absorb heat and so far the results are extremely promising.

“We found that on average the area covered in CoolSeal is 10 degrees cooler than black asphalt on the same parking lot,” said Greg Spotts, the assistant director of the Bureau of Street Services for San Fernando Valley, an area with particularly severe heat problems.

It’s not just about open public spaces either: reducing exterior temperatures has impacts on adjacent interiors. Heat reductions outside and mean cooler spaces inside area homes and businesses. In turn, this can help residents and owners save on cooling costs. It also isn’t just a daytime problem: heat captured during the day is released into the night air, keeping things hotter around the clock.

The process doesn’t come cheap, however: each coat lasts for around seven years but prices out around $40,000 per linear mile. If it works, though, the cost could be offset in part by savings on other fronts, in addition to making for a more healthy metropolis all around. Meanwhile, other strategies are also in play — the city is looking to make roofs brighter, for instance, and bring more green into the mix. (via Inhabitat and L.A. Times, images by Greg Spotts and Giuseppe Milo).