Here in Phoenix, we’re always on the lookout for innovative solutions to extreme heat.
Back in 2020, the city launched a partnership with ASU on a so-called “cool pavement” program. But a few years into the program, the results are, at best, inconclusive.
Amy Cutler, an investigative journalist for Arizona's Family, joined The Show to talk about her reporting on some recent controversies with the cool pavement initiative.
Full conversation
SAM DINGMAN: Amy, good morning.
AMY CUTLER: Good morning. Thanks for having me.
DINGMAN: Thanks for joining us. So first, let's define some terms here when we talk about cool pavement. We're not actually talking about the pavement itself, but rather a coating that is applied to the pavement, right?
CUTLER: Exactly, right. It's that and, and people might have seen it on roads. It's on over 100 miles of roadway across the city of Phoenix. It's that gray silver kind of coating instead of the traditional black top that's on the roads now.
DINGMAN: And so this treatment was a part of a program launched in partnership with ASU. And what did the research at the time promise about this coating.
CUTLER: So the city is quick to tout that at the ground level, that this coating makes the ground up to 12 degrees cooler, which is substantial. But then the issue becomes when you get off the ground and 6 feet off the ground is where there's less of a differential. Researchers found it was just three-tenths of a degree cooler, 6 feet off the ground.
DINGMAN: That is a very large difference.
CUTLER: Yes. Yes.
DINGMAN: And so one of the other major issues there is is reflectivity. Tell us what that means.
CUTLER: Yeah. Exactly right. So the sun that is instead of the, the rays of the sun or energy,, the pa the black top tends to absorb that, that energy. The idea is that the silver or gray coating would reflect it, but unfortunately, that energy doesn't just go away, it's reflected off the ground. So it's absorbed by the homes or buildings around it or researchers found pedestrians walking on the roadway would reflect it or would absorb it as well. And so that can make pedestrians up to five degrees hotter.
DINGMAN: Oh, dear. So if I'm hearing you correctly, while this coating may literally be making the pavement cooler, the people and homes might actually be getting hotter.
CUTLER: Exactly right. Exactly right. So that's why there's been some, some mixed reviews here on what researchers have found.
DINGMAN: And so far the city has spent about $15 million on this program, right.
CUTLER: Yes. $15 million over the last four years.
DINGMAN: And for your piece, you, you went out into some areas of the city where this money has been spent and, and talked to folks tell us what they told you.
CUTLER: Yeah, it was, it was really interesting. There's a lot of mixed opinions about this. Some people really feel like anything the city can do to make a difference here is worth the money. They really were supportive of it. Some even said that they like the way it looked, that it was kind of different and modern. Other people really hated this stuff. They said that they didn't see any difference. They thought it was ugly. They felt like you could see the tire marks on it that it wasn't wearing as well as it should. So lots of different opinions on this and, you know, that's what we found in terms of checking out different spots.
We went to five different locations where the cool pavement had been put down over the last four years and some spots it seemed to hold up a little bit better than other spots. And that was a question we posed to the city too because one of their big claims on this is that because the ground because it makes the ground a little less hot, the infrastructure under the road wouldn't be impacted and so would last longer.
So, they claim that the cool pavement lasts at least twice as long as the traditional black top ceiling. But when we were driving around and, and looking at it, you couldn't really see much of a difference. Just a few years out.
DINGMAN: Gotcha. And since you mentioned going to the city with some of the concerns that have cropped up here, what else did they tell you about your findings?
CUTLER: Oh, so they defended them and said that over time the coating is just gonna fade. But interestingly enough now they are testing another type of cool pavement, a different manufacturer for the coating. And right now the program is on hold because they say that there are some texture and thickness issues. This is the second time this has happened.
So they actually haven't put down any cool pavement the city says this entire summer, which is the, the main time that they do, the, the main paving season. So they haven't put any of the stuff down and they're gonna go with a different manufacturer and they're, they're hoping that the thickness and texture issues will be resolved with this new product.
DINGMAN: And Amy, do we know if this sort of treatment has been effective in, in other cities that deal with extreme heat? Are we just too hot to handle?
CUTLER: Yeah, it's a good question. So when we were looking, Los Angeles actually pioneered this idea. And so they have a lot of cool pavement that's down and they went with the manufacturer that the city of Phoenix is switching to. And so they have had some success.It hasn't been as widespread there as it is in Phoenix. And I should also note that other cities, you know, are taking note of this and there are other cities that are starting to use this cool pavement.
I think that there's a big feeling out there that while the research into this is, is new and mixed, it is just getting so hot that pe you know, these cities want to do something, they want to address the issue and, you know, at surface level, it seems like it would be a good idea, right? You know, 12 degrees hotter on the ground seems like, you know, win win. It's just when you kind of take a closer dive into this where you realize that there are, you know, it might not be as good as, as, you know, how, what it seems, I guess.
DINGMAN: Gotcha. And, and last question for you, Amy, you mentioned that the program is currently on hold. Do we have any sense of how soon we might get an update on, on the possibility of this, this new manufacturer?
CUTLER: Yes. So the city says that they are gonna start putting down this new coating later on this month in August. But I should point out I started asking questions about this back in May and at the time, they said that it was gonna, you know, they were gonna start putting it down in June then it was July. Now it's August. So I don't have an exact sense of what the holdup is. I mean, if they're just trying to get the product or if they're trying to do some more testing or what the situation is, but they are saying that they are planning to put down more cool pavement later on this month.
