What is cool pavement?
It is a water-based asphalt treatment that is applied on top of the existing asphalt pavement. It's made with asphalt, water, an emulsifying agent (soap), mineral fillers, polymers and recycled materials. It contains no harmful chemicals and is compatible with traditional asphalt.
Why would Phoenix apply cool pavement?
Asphalt collects and retains heat during the day and releases it at night. Phoenix is among several cities that are experiencing the urban heat island effect due to the retention of heat within the built environment. U.S. Environmental Protection Agency data shows the difference in nighttime temperatures in heat island areas can be as much as 22 degrees warmer than temperatures measured outside the heat island. Higher nighttime temperatures lead to more energy consumption, more greenhouse gas emissions, air pollution and other harmful effects.
Cool pavement reflects back the sunlight that hits it. Because the surface reflects rather than retains heat, cool pavement has the potential to offset rising nighttime temperatures in Phoenix. The use of cool pavement technology may help reduce the heat island effect and reduce temperatures in the city. It is also useful to cool neighborhood areas that don’t have much shade from the sun.
Phoenix participated in a workshop hosted by the federal government and the City of Los Angeles. Los Angeles has been using cool pavement on neighborhood streets and has reported positive results in reducing roadway surface temperatures.
How did this program get started?
The Street Transportation Department is always looking for ways to improve what it does and improve the livability of the city. Phoenix wants to test the cool pavement technology and material to see whether it is effective at reducing temperatures in Phoenix's desert climate. City staff engaged university researchers to take measurements and collect data over several years. You can learn about the first year scientific testing by looking at the September 14, 2021 video on this page. Continued study will determine if the cool pavement product mitigates the heat island effect and if those effects are sustainable over time.
The department also wants to learn how the product holds up. The Phoenix climate is unlike other major cities. We want to make sure it
will last through our 300 days of sunshine, monsoon storms, high temperatures and daily traffic.
In October 2021, the pilot program ended and cool pavement will become a regular program for the city's Street Transportation Department.
Where are you testing cool pavement?
The Street Transportation Department identified local streets in each City Council district for cool pavement treatment. Since different parts of the city experience different rain, monsoon conditions, and degree of wear on the pavement, it should be a good way to find out how well it is working and how durable it is.
The streets selected for the pilot project had asphalt that was in good condition but where a preservative surface treatment was warranted. Preservative treatments extend the life of the road by sealing any surface cracks to prevent moisture intrusion and improve the overall road condition and appearance.
How can my neighborhood get cool pavement?
Pavement condition is one of the key criteria for future installations. We will also try to solve community challenges such as providing heat relief to areas with very little shade. Future installations will be studied to ensure the cool pavement is placed equitably and in areas where the immediate benefit is most needed – such as areas with little or no shade or areas where people move on foot or bicycle out of necessity. Cost will also be a consideration, as the city works to use taxpayer funds wisely.
While the cool pavement material is more costly than the seal coating materials we usually use, results from other cities suggest the material is effective and longer lasting than traditional asphalt seal coats. If that’s true in Phoenix, and the material provides the environmental benefits we believe it will, you can expect to see wider use of cool pavement when neighborhood streets are due for pavement maintenance.
Can I buy the cool pavement material and treat my driveway with it?
Most Phoenix driveways are concrete, so it's unlikely the product would work for that application. The product is formulated to bond to underlying asphalt, and it’s also applied with specialized equipment over a larger area. There may be other types of coatings available – such as those used on concrete around pools – but they are probably not meant to handle vehicle movement.
Does cool pavement look different than traditional asphalt?
Yes, the cool pavement coating is a lighter grayish concrete color. The material cures to a matte finish. Most people consider the finished appearance to be similar to aged concrete.
Is cool pavement safe to use?
It is safe for all types of vehicles, pets, people and all the typical activities that would take place on a road. Despite being lighter in color, cool pavement does not result in glare once it has cured in place for a few days. It also meets or exceeds skid safety requirements.
Is this a new product?
Colorized seal coats and asphalts have been around for a while. Cool pavement uses existing material and technology in a new way.
How is cool pavement applied?
It can be sprayed or applied with a squeegee, just like the other surface treatments we apply to city streets. Phoenix actually pioneered the spray method allowing for large areas to be coated more efficiently and with less hand labor.
Is there a difference in skid resistance between regular asphalt and cool pavement?
A friction test was conducted with the Arizona Department of Transportation (ADOT). The friction test was conducted at 40 MPH. While there are no established standards for skid resistance on 25 MPH neighborhood streets, the Street Transportation Department saw value in conducting a friction test as a baseline for future evaluations. The test measured friction in wet conditions. Staff found no safety concerns for people walking, driving or bicycling on streets coated with cool pavement.
Where can I see cool pavement?Map showing completed cool pavement installations
Since 2020, the cool pavement seal coat has been applied to multiple quarter sections of neighborhood streets citywide and the parking lot in one city park.