The primary factor in midcentury urban planning and subsequent flight to the suburbs involves what was then America’s biggest industrial product: the automobile. Highways shortened commutes, encouraged travel, and carved out new neighborhoods (for better or for worse), while creating traffic patterns that still exist to this day.

Now that residents are considering alternate modes of transportation—for speed, for exercise, for the environment—it’s time for a judicious look at car-dependent cities. In Honolulu, local business owners see a new bike lane as a means for saving sidewalk commerce, while Phoenix struggles to adapt to walking and biking under a steadily-intensifying heat dome.

Ambient video for Phoenix

Phoenix

It is 109 degrees Fahrenheit when I first step onto Phoenix’s Central Avenue. As I take in the first block of what my phone tells me should be an easy nine-minute walk, I see seemingly infinite lanes of asphalt, vast empty sidewalks, and not a sliver of shade.

A few weeks earlier, a high-pressure system that meteorologists christened a “heat dome” had parked itself over the aptly named Valley of the Sun, producing a string of record-breaking temperatures across the state. It was part of a global trend that would lead climatologists to declare 2016 the hottest year in recorded history.

Soon it will be hotter. According to a study published by Nature Climate Change, Phoenix is one of the U.S. cities that will see an exponential increase in the number of 100-plus degree days by the end of the century. An estimated 162 days per year will see temperatures over 100. That means for almost half of the year, it will not just be dangerous for humans to be outdoors, it will be deadly.

I tried to envision this future while walking south on Central, when I started to have a strange sensation, as if I was treading on gum. It was so hot that I could feel the heat of the street radiating onto the soles of my feet.

It’s right about then that I see the biggest challenge facing Phoenix: How do you foster a walkable urban core when the pavement melts your shoes?

On the distant horizon, the train shimmers into view, so out of place that it’s like a mirage. Incredibly, this city of wide streets and suburban sprawl has also nurtured one of the biggest public transportation success stories in the U.S.

Within a year of Phoenix’s light-rail system opening in 2008, ridership had surpassed predictions by one-third. In April of 2016, the system was serving about 54,000 weekday riders, a figure that planners had not expected to reach until 2020.

Riding the light rail—which is, blissfully, air-conditioned—south into downtown, Phoenix is a blur of blue sky and beige buildings. Central Avenue traces a spine along the length of the Phoenix metropolitan area, running uninterrupted for about 20 miles.

It’s not hard to locate it from anywhere in the valley because it’s pretty much the only street that has consistent density: a sandstone canyon of mid- and high-rise structures, set back from the street, the rippling blacktop of parking lots radiating around them.

It’s a visual reminder that, even for all the city’s transit victories, Phoenicians are still firmly stuck in a car-first mindset. I see this in action when I go to lunch with Grady Gammage, Jr., author of The Future of the Suburban City: Lessons from Sustaining Phoenix and an unapologetic booster of the city.

I meet Gammage at the Central Avenue fixture Durant’s, a flocked-wallpapered 1950s-era bunker that feels like it was erected specifically as an antidote to Phoenix’s relentless sun: dim lighting, cool leather banquettes, iceberg wedge salads.

Since I’m arriving from the light rail station, I enter using the front door. “It occurs to me that Durant’s is a perfect metaphor for changes in Phoenix,” Gammage says, laughing. “No one has used the door from the street for decades. It’s been the entrance from the parking lot and through the kitchen that mattered. Maybe now, with light rail, that’s changing.”

We ask the hostess how many people use the front door now. She estimates I was the fifth person this year.

I blink in the late afternoon glare as I stare down Central, squinting at what I think is the local bus. Sweat streams down my forehead as I attempt to align my body with the shade of a telephone pole.

The Heat has become a secondary character during my visit, a nefarious meddler mentioned in nearly every conversation. We can’t eat outside due to The Heat. We should wait until The Heat dies down. How are you coping with The Heat? So when I show up on a Monday evening for the weekly walk event Meet Me Downtown and the temperature is still hovering at 102, my expectations for encountering any fellow participants are very, very low.

How do you foster a walkable urban core when the pavement melts your shoes?

Yet here they are. At 5:00 p.m. on the dot, there are dozens of Phoenicians circling the back bar at Copper Blues, on the corner of Central and Jefferson. Some in Spandex and Nikes, yes, but many in work wear and sensible walking shoes.

“Why wouldn’t people walk in Phoenix?” asks Joseph Perez, the city’s boisterous bike coordinator, who has every reason to be bullish about the city’s potential.

The Phoenix native is helping to fulfill a comprehensive complete streets mandate from Mayor Greg Stanton, laying down the bike and pedestrian infrastructure that will get people out of their cars, and hopefully onto the city’s sidewalks and nascent bike-sharing system, Grid.

“The challenge in Phoenix is the engineered streetscape and connectivity,” he says. “We used to have buildings with canopies. Now we have developers who build rows and rows of single-family homes that make walking to the store or school a lengthy experience. We need to be more mindful of how complementary land uses should connect.”

As we head up Central, he shows me how Phoenix had designed solutions for keeping pedestrians cool for nearly a century. On a handful of the city’s oldest buildings, there are still some covered pedestrian arcades and evidence of awnings that once stretched the width of a sidewalk.

We stop in the lobby of the Hotel San Carlos—the first fully air-conditioned hotel in Phoenix when it was completed in 1926—where a grainy film of Central Avenue (then Center Street) in 1930 plays on a tiny screen: Pedestrians stride across the bustling block, and a streetcar rattles down the middle. By 1948, the streetcar was abandoned.

And in 2016, a summer evening walk in downtown Phoenix means we must incorporate contemporary versions of cooling infrastructure, hopscotching from public plaza splash pad to pool deck with patio misters to a cavernous speakeasy-like bar that is literally underground.

At first, I feel like I’ve signed up for a SoulCycle class held in an industrial furnace when I join a group bike ride later that evening. But of all the transportation methods that are not particularly well-suited to The Heat, a bike seat offers several benefits.

The terrain is mostly flat, which means minimal exertion and a built-in breeze. The city is a grid so it’s easy to navigate. And two-thirds of the year—or so I hear—the weather is absolutely perfect.

These sentiments, as well as some criticisms, are echoed by my fellow cyclists, like Karen Voyer-Caravona. She started the blog She Rides a Bike after moving from Flagstaff to document her adventures on a Brompton folding bike.

“I’m not ready to categorize Phoenix as a great place to walk or bike,” she says. Not that it’s dangerous, but because the city hasn’t yet made a sweeping gesture to people like her.

“Phoenix needs to go all-in with bike and pedestrian infrastructure,” she says. “We obsess about creating abundant parking but not safe streets. We have very wide roads, carrying lots of cars, at a high rate of speed. Or we have very wide roads, carrying not that many cars.”

As we ride, Central provides the perfect illustration for the problems that Voyer-Caravona outlines. We easily swarm a lane of traffic, the light rail pulling ahead of us like a pace car. The roadway, which is up to six lanes wide at some points, gives cars plenty of room—maybe too much room, I think, as cars careen by. But during much of our ride, Phoenix’s main street is completely empty.

At the northern edge of Phoenix’s downtown, at the center of a large park, Central Avenue reaches a very gradual apex. It’s more like a knoll, and unless you’re pedaling a bike or really paying attention as the light rail rolls over it, you’ll barely notice.

Central Avenue has always been a testing ground for transportation innovation.

Below this nearly imperceptible rise is the I-10 freeway, which is, for the most part, an unremarkable, very wide interstate. But in 1990, it was tunneled underground for about six blocks here to create Hance Park, preserving cultural institutions, historic neighborhoods, and invaluable green space.

It’s a reminder that Central Avenue has always been a testing ground for transportation innovation. And you can see that best in a revised vision for Phoenix’s transportation future, the T2050 plan. In 2015, voters approved the plan, which includes major transit investments as well as 1,080 miles of bike lanes and 135 miles of sidewalks.

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It also means an extension of the light rail, which is critical because it will finally connect Phoenix’s most transit-dependent residents to jobs, says Silvia Urrutia, director of housing for the Raza Development Fund, which helps finance developments for Latino and low-income families.

Because the light rail first opened at the height of the recession, there was little to no speculative development tied to transit. “We were the only people building,” says Urrutia.

Which was good for affordable housing, but bad for the overall density the corridor needs. Now Urrutia has the ability to plan ahead—she’s working on an 82-acre former brownfield on Central near the Salt River which will become Plaza de las Culturas, a sustainable mixed-use development with schools, housing, and small businesses that will provide a physical hub for the community.

The question that keeps the project focused: “How can we connect what we’re doing with the rail?”

On its very hottest days, the desert acts like a vacuum, sucking in humid air from the coast. This is called “monsoonal moisture,” and can manifest as extreme weather events, like brief torrential rainstorms called microbursts.

When I see the dark curtains descend upon the city, I tilt my face up, expecting the first drops of liquid refreshment from the sky. Instead my cheeks are slapped with sand. This is a haboob, Phoenix’s version of a dust storm, where swirling walls of dirt preface the sheets of water.

Incongruously, about half of Phoenix’s annual rainfall falls during its warmest months, but because it falls so fast, most of it disappears as urban runoff (the kind that meanders into dry washes and can cause flash floods). On many streets there are several inches of standing water, spraying high arcs onto the sidewalk as I ride my Grid bike over the steamy asphalt.

The best place to see how a swatch of green changes everything is at the corner of Central and Taylor. Civic Space Park acts as a giant rain garden, allowing water to slowly percolate back into the ground.

It’s also one of the few spots on Central you’ll see inviting grass and feathery trees as well as an aggressive shade program: a series of contemporary pergolas cover the sidewalks, Grid bike kiosks, and Arizona State University’s main light-rail station.

This type of “engineered shade” is a big topic in town, and no one thinks about it more than the city’s arborist, Richard Adkins. He thinks Central represents the biggest opportunity in Phoenix.

Although parts of the street are well-shaded, most of Central is lined in ornamental palm trees—some of which are historically protected—that are too tall to provide much relief. But the solution isn’t simply to fill in the gaps with more trees, says Adkins. What Central needs is a true desert canopy.

To maximize the shading effect as well as the sparse resources, Adkins envisions Central’s shade being clustered into what he calls “plant guilds.” Plant guilds are better for conservation—watering several plants at once makes far more sense than dispersing it across a quickly evaporating atmosphere—and for budget-strapped maintenance.

But it’s also about permaculture: orchestrating specific, customized ecosystems that help each species thrive. “It’s oases,” he says. “That’s how deserts work.”

On my way back to Central, I recognize a velvet mesquite, the city’s most common tree, from an illustration in Adkins’ office. The tree looks scruffy, but standing beneath it, the air is unmistakably cooler.

I pause, just long enough to imagine this version of Central. Medians as wildlife habitats. Intersections as planted parkways. Transit stops as microforests. Refreshed, I continue my journey.

Alissa Walker is the urbanism editor at Curbed. She lives in Los Angeles where she loves to take the train, ride bikes, and walk. Follow her at @awalkerinLA.