The city of Los Angeles is testing a unique grey substance designed to keep roads cooler by 11F-13F. The $150,000 pilot project in 15 council district aims to keep surrounding homes cooler as a result. A CoolSeal coating could cost an estimated $40,000 per mile and last seven years. Average temperatures in Los Angeles have risen 5 degrees in the past 100 years on account of the heat island effect produced by miles of asphalt freeways, roads, parking lots, roofs and more, climatologists say. In summer, temperatures have risen an average 10 degrees. Los Angeles, August 14, 2017. Photo by Lionel Hahn/Sipa USA(Sipa via AP Images)