What’s So Bad About … Pavement?

In 1894, according to Vineyard historian Chris Baer in his book Martha’s Vineyard Tales, the New York Times published a story celebrating the Island’s concrete roads, at least 40 miles of them around Cottage City. These roads, the paper of record declared, offered a cyclists’ paradise, the best in the country outside of Washington, D.C. These days, few would cite pavement as a signature feature of Martha’s Vineyard. And most of us like it that way, proud of the dirt roads that zig and zag the Island.

But those dirt roads carry benefits beyond slowing down drivers and preserving a rural vibe. Pavement holds heat, creating what’s called the Urban Heat Island effect (UHI), which is not just uncomfortable for residents but potentially deadly. As a result, urban planners are looking for ways to mitigate this effect. And a movement that aims to “depave” parts of towns and cities is taking things even further — to remove an unhealthy built environment and replace it with green space that combats the UHI effect and also contributes to the social health of a community. 

Phoenix, Arizona

While you might not know that a pavement temperature of at least 158°F is required to fry an egg, the folks in Oatman, Arizona do. Each July 4, the  town hosts its annual solar egg frying contest, so “hot enough to fry an egg on the sidewalk” isn’t just hyperbole for them. But just 200 miles southeast of Oatman is Phoenix, where a new pilot project is actively working to make egg frying on asphalt difficult if not impossible — by creating what’s called, appropriately enough, “cool pavement”. 

In Phoenix, which has more than 300 days of sunshine and temperatures that routinely top 110°F, street surface temperatures reach up to 180°F, says Spencer Blake, a public information officer for the city. That’s not only unpleasant and unhealthy, it can be deadly.

This UHI effect disproportionately affects lower socioeconomic communities and marginalized people, and Phoenix is taking an innovative approach to tackle it.

The city began its pilot project in 2020 to apply a reflective coating to asphalt to eight neighborhood streets and one park, all due to undergo routine maintenance. The water-based treatment is a mixture of asphalt, water, mineral fillers, polymers, and recycled material. There are no harmful chemicals that will run off the surface onto green space or waterways, says Heather Murphy, who works in Communications and Public Engagement for the City of Phoenix Street Transportation Department. 

“We’re using a product that’s 100% compatible with the asphalt so that when it reaches the end of its useful life, we can mill it, filter it, grind it into new asphalt, and repave with it,” she says. Consequently, not only can the city combat the Urban Heat Island effect, Murphy says, “we’re buying less raw material.” 

The pilot project has expanded to add another eight new neighborhood streets that were scheduled for maintenance. The “cool pavement” isn’t designed for the high-traffic areas of main city streets or freeways. But, says Murphy, “where do people walk their dogs, stroll with their children, or play a pickup game of basketball? They do that in their neighborhoods.” 

According to Spencer Blake, results from the pilot showed a successful reduction in street surface temperatures of between 10°F and 15°F. The coating is more expensive than what the city typically used but, says Blake, indications are that it is more effective and longer lasting. 

But tackling the UHI effect was also about “livability” of neighborhoods, says Heather Murphy. That might take longer to determine, she says. 

In the meantime, Phoenix, which boasts it has among the largest areas of cool pavement in North America, is fielding calls from cities around the country looking to try a similar approach.

“The main question we get,” Murphy says, “is where can I get it.”

Portland, Oregon

Nobody needs to convince Katherine Rose or Katya Rehna of the value of local projects that can be replicated in other communities, or of the importance of engaging the community stakeholders in recreating their spaces. 

The two make up the staff of Depave, a sort of ground zero for the deconstruction movement. Depave began in Portland, Oregon, in 2008 with a simple conclusion: Pavement is the problem. The solution, therefore, was to depave, to remove pavement where possible and replace it with nature. 

“We were kind of the first organization to coin the term ‘depaving’ back in 2008,” says Katherine Rose, Communications and Engagement Coordinator with Depave. Since then, Rose says, the group has trained and “empowered” other groups to take a similar model, currently at work with a group in Chicago. 

The objective is straightforward. “The depaving movement is seeing an empty parking lot and thinking … What else could exist there? What else could provide for a community? A garden? Could it help filter water and slow water from entering our stormwater system? Could it be a living space rather than just a place for us to literally park cars?”

The group works a lot with schools to rethink its playgrounds, which are often paved surfaces. “There is a whole Urban Heat Island effect,” Rose Says. “We’re actually making [these spaces safer, especially as we’re dealing with record heat waves moving through our communities.” 

Rehna points to the emotional impact of green space. “There are dozens of studies that show that happiness increases, mental health increases. When stores get a tree in front, they tend to get better business.” School employees have told Rehna that they use their depaved spaces to take kids outside if they’re having a bad day. “They’ll sit them outside and have a conversation outside of the building,” Rehna says. She’s not surprised at the impact. “To be able to get a breath of fresh air for a second and be in a safe space to do that, to be surrounded by native plantings and trees is just conducive for healthier conversations, and lowering stress in general.”

The reasons communities decide to depave is varied. Some are having flooding issues, stormwater management problems, Rehna explains. Sometimes, it’s just that it’s really hot; there’s no shade. “No matter what your entry point is,” she says, “you’re going to end up with environmental, social, and economical benefits.”

Reyna and Rose are adamant about engaging with those most affected, expanding their own community outreach and partnering with other groups who can help. “We’ve definitely been prioritizing projects to make sure we’re serving communities that have been historically disenfranchised,” Rehna says. Social justice is a key pillar of the depave movement. 

Depaving isn’t just about getting rid of the pavement, it’s about what replaces it. Biodiversity is a key part of Depave’s projects — native plantings, pollinator habitats. “By creating these niches within an urban space, you’re helping promote biodiversity across the space,” Katherine Rose says. It’s, literally, a grassroots approach. “We’re adapting urban landscapes to be more livable,” she says. “And by doing that, we’re questioning structures in place like pavement, and rethinking how we can use that space.”

Chelsea, Massachusetts

The tiny 2.5 square mile town of Chelsea might not have the relentless heat of Phoenix, Arizona, but there’s one block at least for which summer heat is magnified, often 20° hotter than elsewhere, according to data collected by Boston University, which placed temperature sensors in trees and on roofs. The problem? “A lot of asphalt and concrete,” says Maria Belen Power, Associate Executive Director of Green Roots in Chelsea, which focuses on environmental justice. “When folks are experiencing average summer days in our region, our community in Chelsea is experiencing much hotter temperatures…that exacerbate public health concerns like upper respiratory illnesses [and have] real consequences on people’s lives,” she says.

Green Roots chose one block to revitalize, consisting of a vacant lot, a Boys & Girls Club, 10 multifamily dwellings, parking lots, and five trees. Five. And asphalt. Lots and lots of dark asphalt. 

The plan included removing much of the asphalt and replacing it with open green space and trees, and covering the roof of the Boys & Girls Club with white reflective coating. The project enlisted the city of Chelsea, the Department of Public Works, and the Boys & Girls Club, all working together. “Including the folks that are most impacted by the issue is a critical part of our work,” Power says. “We wouldn’t be doing this project without the residents that live on that very same block.” Consequently, residents were invited to share their ideas of what they wanted, including a design contest to reimagine the space. 

While the work continues to be underway, to date the block has 47 new trees — crabapple, cherry, elm, and hawthorn. Sidewalks have been replaced with planters, porous paving stones, or white concrete. Where asphalt is necessary, it is gray rather than black. 

Success is measured not just in how many degrees cooler the space becomes but also the impact on people’s emotional state, their mental health. “How do people feel who live there, who work there, who walk around there? That’s pretty critical,” Power says. 

Power is acutely aware that this is one block in one small city in one state. But these hyperlocal projects matter, she says, and they create templates that can be replicated. “It gives us a lot of hope that we can create incremental change and we can improve public health.” But that, of course, is not enough, she says. “Hyperlocal pilots like this alone are not going to move the global needle. We need to be addressing climate change, at every level.”