When I was in Phoenix this past spring I noticed a number of people carrying their big dogs around. At first I wasn't sure what was going on. I thought maybe the dogs were injured and couldn't walk. But then it dawned on me that maybe the ground was too hot for the dogs to walk on it. Phoenix is kind of hot sometimes and so this appears to be a thing.

In response to this kind of hot problem, the city has a pilot program underway where they're testing out something that they are calling "cool pavement", which is essentially a highly reflective coating that gets layered on top of your traditional asphalt streets. Here's a video showing some of it getting applied:

The idea here is, of course, to lower the surface temperature during the day and also reduce the overall urban heat island. And after the first year of the pilot program, the results have been encouraging. Cool pavement had an average surface temperature that was 10.5 to 12 degrees Fahrenheit lower than traditional asphalt during the middle of the day.

But there have been some tradeoffs. Because of its higher reflectivity, mean radiant temperatures increased by about 5.5 degrees Fahrenheit during the day, which means that these streets feel warmer to humans when they're around them. That's obviously not ideal, but it could be a necessary trade-off to reduce surface temperatures across the city.

For more information on Phoenix's cool pavement pilot program, click here.