No matter how detailed the plans, there’s no way to know for sure if a new idea will work until you give it a try. That’s especially true with something genuinely novel -- like putting a forest on top of a downtown freeway.

More than a half-century ago, the city of Akron, Ohio, built a highway called the Innerbelt into its downtown. Like a lot of freeways created during that era, it destroyed some neighborhoods while cutting off others from the center of the city. In terms of handling traffic, it turned out to be unnecessary. Akron’s population is down by a third from its 1960s peak. A road meant to carry 120,000 cars a day ended up being used, even on busy days, by maybe a fifth as many.

The city shut down the freeway a couple of years ago. That left the question of what to do with the land. A designer named Hunter Franks threw a big party, hosting a meal on the Innerbelt for several hundred people. Franks polled those who showed up, and they overwhelmingly said they favored turning the land into some kind of green space.

It wasn’t that outlandish. Atlanta and New York have enjoyed huge success in turning old rail lines into elevated parks. Dallas and other cities have placed parks on top of working freeways. Still, Akron officials were not sold on the idea. They worried about the logistics of letting kids play in close contact with the active roads that were still connected. But Franks received a grant from the Knight Foundation that allowed him to proceed anyway.

At first, the city insisted that he plant trees in pots, so his “Innerbelt National Forest” would be easier to remove. In time, he was allowed to plant them in the ground, while also putting in a stage, a children’s play area, a mulch trail and other amenities. The park, which opened in August, was an immediate hit. Although it was originally seen as temporary, talk soon started up about extending its life, or even making it permanent. “Some or all or most of it may end up staying,” says Jason Segedy, Akron’s planning director.

Residents, posting pictures of the park on Instagram, keep comparing it to an old Joni Mitchell song, noting that it’s the reverse of her 1970 lyric about paving paradise to put up a parking lot. The fact that a disused freeway can become a pop-up forest makes it easy to envision turning practically any area into green space, Franks says.

The crucial thing was seeing it work in real life. It’s one thing to try to imagine how a park might work when staring at plans, but it’s an entirely different matter watching kids play there, or seeing people enjoying performances on pleasant summer evenings. Governments are good at holding meetings and soliciting proposals to imagine how something might work, but there’s value in simply letting people use a space and allowing their behavior to inform a more permanent plan. “I like the idea of trying these kinds of things,” Segedy says, “hitting on elements that people find compelling that we can recreate or use.”