An estimated 10 percent of Los Angeles is covered in asphalt thanks to the city’s sprawling network of roads and parking lots. On sunny days, the heat retained by these paved surfaces can make neighborhoods feel far hotter than those in more rural areas — a phenomenon known as the “urban heat island effect.” Now, Los Angeles is experimenting with painting its pavement grey to help significantly lower temperatures.
The city is using a material known as CoolSeal, a grey-colored coating that reflects solar rays, compared with dark asphalt, which absorbs them. A similar material is used on taxiways and pavement where military spy planes are stored to make them less visible to satellites using infrared cameras, according to The Washington Post. In preliminary tests, areas of pavement covered in CoolSeal measured an average 10 degrees cooler in summer months than those covered in black asphalt.
Los Angeles is now testing the grey coating in 14 of the city’s 15 council districts, according to The Washington Post. Over the next several months, officials will be studying both how the coating reduces heat and whether it distracts drivers. The coating costs about $40,000 per mile and lasts seven years.
The experiment is part of a wider city initiative launched by Los Angeles Mayor Eric Garcetti to reduce its average temperature by 3 degrees Fahrenheit over the next 20 years.