In May, officials in Los Angeles held a news conference to tout the new “La Sombrita,” a pilot design intended to add some shade at four of the city’s bus stops.
The 26-inch-wide teal perforated slab of metal was instantly mocked on the internet. Many couldn’t see how the slim structure, which was meant to provide shade for maybe one or two people on sunny days, could live up to its promise. A “full-scale takes bonanza” ensued, “lobbing criticisms that ranged from sort-of unfair to divorced from reality,” wrote Bloomberg CityLab.
Disastrous rollout aside, LA had been trying to address a crisis traditionally overlooked in city planning: dangerously hot public spaces. Bus stops are one example of the city’s many mini heat islands that experience higher temperatures in the summer, posing a danger to children and adults stuck in the sun. Jennifer Vanos, a heat researcher at Arizona State University in Phoenix, has measured bus stops that have exceeded 160 degrees Fahrenheit in the direct sun.
Bus stops aren’t the only parts of cities that overheat. Sidewalks get hot too. And a slide in a sunny playground can easily exceed temperatures that burn skin in a matter of seconds.
A solution, as cities race to adapt to climate change, is adding shade, and a lot more of it. That means trees, tarps, vertical or horizontal structures — anything to help block the sun’s rays. But La Sombrita’s debut demonstrated the solution is harder to implement in practice.
Heat inequity is dangerous
The urban heat island effect, which refers to cities being hotter than surrounding rural areas, doesn’t quite describe the wide range of heat experienced within a city.
Air temperature alone fails to capture “the human experience of heat,” said Dr. Este Geraghty, chief medical officer of ESRI, a digital mapping company that has worked with National Oceanic and Atmospheric Administration to understand urban heat. Geraghty explains there are a range of factors that can make a person feel hotter: an individual’s health; whether they are acclimatized, meaning their body has adjusted to hot weather; whether they are in a park or on a sunny sidewalk; and whether it’s dry or humid.
It’s the perception, more than the temperature reading, that matters most in heat-related illnesses, including symptoms of heart disease, lung disease, and mental health. The problem isn’t just a short-term heat exposure, but lacking the chance to cool down.
Urban heat is also worrisome, because cities are hotter overnight than their rural surroundings. The urban heat island effect is at its worst when concrete and asphalt radiate heat absorbed during the day back out when the sun’s down.
“Long-term lack of relief makes it harder for people to use their physical resilience and body makeup to help them fight the effects of heat,” Geraghty said. “It’s like banging on them over and over again.”
Even within short distances, a city’s microclimates can vary dramatically. But when a person has to walk to a bus stop in the full sun, then wait up to 30 minutes for the next bus, or a child is playing during school recess, that relief may never come.
They also might not get that relief at home. Neighborhoods that are predominantly Black and brown have fewer trees that provide shade and natural cooling, due to historical redlining. And that environment of asphalt and concrete, in the direct sun, can turn a summer heat wave into a dangerous, even deadly event.
And many public spaces, instead of providing an escape, are notorious for worsening the experience of heat.
Bus stops, playgrounds, and sidewalks expose people to astronomically high heat
Shade helps provide some of that relief, but it’s often lacking in public spaces where people are spending time midday. Those tend to be bus stops, playgrounds, and sidewalks en route to public transit that have no shade from the sun.
Playgrounds, according to Vanos, are a particular challenge. In Phoenix, she has measured surfaces of slides, swings, and rubber surfaces compared to shaded surfaces.
On a 100-degree day, a slide facing the sun can measure up to 160 degrees, she found. That can burn the skin just five seconds.
Vanos’s thermal camera shows how different qualities of shade make a difference. Even partial shade is better than nothing.
There are national guidelines for playground safety that dictate modern playgrounds should be constructed with certain materials, such as plastic and rubber. The surface of the playground needs to be soft to cushion any falls, so it is usually rubber or artificial turf, rather than grass. After accounting for all these concerns in playground design, Vanos explained that adding shade is often an afterthought.
Bus stops have their own problems. The image captured by Vanos shows how a 100-degree bus stop can actually be 30 degrees higher because it is in the direct sun:
To get a better understanding of how to improve and intervene in public spaces, cities have partnered with heat researchers and NOAA to get to the bottom of where their heat is worst.
Since 2017, NOAA has run an annual Urban Heat Island mapping program that sends volunteers out with heat and humidity sensors to take temperatures all over the city by bike or car. Morgan Zabow, community heat and health information coordinator at NOAA, said the data is collected over a single day, but ends up forming a snapshot of the inequities around a city. By the end of this summer, 75 communities will have collected and mapped this data.
Las Vegas is one of program participants that has used the data to start making interventions. The city plans horizontal, slimline shelters (named for their low profile) at 100 bus stops in the hottest areas, and plans to eventually expand that to 80 percent of hotter neighborhoods.
The solution seems cut and dry: Once cities map where it’s hottest, they should just add more shade. Unfortunately, it’s harder than that to get shade where it’s needed.
Why can’t we just have more shade?
Cities are getting better data to understand which public spaces are especially hot. And they’re using it to find interventions, but it’s often easier said than done.
The first challenge is: What kind of shade? Shade comes in many flavors. Trees provide many more benefits than just shade, such as cleaning air and cooling spaces, but aren’t the solution everywhere. Trees, planted now, won’t be useful for shading for another 20 or 30 years, so they are hardly a short-term solution for the heat. Also, not every space is equipped to handle a tree, due to competing power lines, pipes, and other common structures of the urban landscape.
Bus stops face some of the same problems; planners need to think about visibility of pedestrians, safety, sidewalk width, and competing structures. The approval process for a bus shelter can be restrictive and imposing in some states and cities. That was a situation LA ran up against — La Sombrita’s design was limited to shade that could be created vertically and would have a slim profile.
Sometimes the solution isn’t always in design. “One approach is really actually just having more frequent bus service so that someone isn’t spending as much time waiting for the bus,” said Alex Engel, senior communications manager of National Association of City Transportation Officials. “If that bus is coming every 30–45 minutes, that might be intolerable. But if you have a fast, frequent bus network where the bus is coming in [15 minutes] or less, you’re only waiting a few minutes.” Funding more public transit overall, even if it’s not directly targeted at addressing heat, can indirectly help.
Just as there are many different flavors of heat, there are many different kinds of shade. Vanos explained there’s vertical shade — when a wall casts shade — or horizontal shade, made by a sail or roof. Sometimes a space only accommodates partial shade, angled to provide shade for part of a day. Urban planners can look at these shade structures in the short-term to help cope with the heat. That buys them time to find more effective solutions, including bringing more greenery and trees into public areas.