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Los Angeles Tests Reflective 'Cool Pavement' On Streets (dailynews.com)
mikeebbbd writes: As reported in the Los Angeles Daily News, during the current heatwave various officials swooped down on streets coated with an experimental light-gray sealer that makes the old asphalt into a "cool street" -- and it works, with average temperature differences between coated streets and adjacent old asphalt around 10F. At a large parking lot, the temperature reduction was over 20F. If the material holds up and continues to meet other criteria, LA plans to use it on more pavement rehab projects, which could eventually make a difference in the heat island effect. The "CoolSeal" coating is apparently proprietary to a company named GuardTop LLC, costs $25-40K/mile, and lasts 5-7 years. At that price, it's might not be used a lot, at least at first; typical slurry seals run $15-30K/mile.
Might be cheaper to plant trees and landscaping in an urban environment.
That is absurd. There is absolutely no way you are going to plant trees along a mile of urban roadway for $25-$40k. You need to add at least two zeros. Even more in LA where no plant life survives without water, so you would need to trench for irrigation pipes, and pay for ongoing maintenance.
Concrete is much more expensive than asphalt. It's also harder to install and maintain. While slabs of concrete may last longer, it doesn't do much good if it becomes irregular (kathunk kathunk kathunk .. for 100 miles). It can't be resurfaced as easily (no grinding down the top and pouring 2 inches of additional concrete on top) as asphalt either. It has use cases on grades that are steep, or where heavy travel craters the asphalt in hot areas (stop lights, downhill braking, etc).