From Portland to Melbourne to Paris, city planners are dreaming of—and, in some cases, creating—the “15-minute city.” But while many are rejoicing in the potential for greener, safer, kinder spaces, others warn that such visions are blind to equity issues—especially if affordable housing is lacking.

“At its heart is the concept of mixing urban social functions to create a vibrant vicinity,” complex systems analyst Carlos Moreno told Bloomberg Businessweek. This pattern, both lively and neighbourly, would be “replicated, like fractals, across an entire urban expanse.”

As the City of Paris’s special envoy for smart cities, Moreno is overseeing the transposition of the 15-minute template—dedicated to ensuring that citizens are never more than 15 minutes on foot, bike, or public transit from everything they need to live, work, and play—onto a city that is already far more pedestrian and corner store friendly than many others in the developed world.

The allure of (re)building cities into welcoming, interconnected neighbourhoods is growing stronger even in car-centric places like Detroit, as the triple threats of the coronavirus, political upheaval, and climate change leave many calling for “a return to a more local and somewhat slower way of life, where commuting time is instead invested in richer relationships with what’s nearby.”

Crises such as the one currently striking in cities worldwide “show us the possibility for rediscovering proximity,” said Moreno. “Because we now have the possibility to stay closer to home, people have rediscovered useful time—another pace for living.”

And the allure of the 15-minute city concept is growing. A July report from the C40 Cities Climate Leadership Group celebrates the model as a central pillar in urban pandemic recovery roadmaps.

“Paris is far from alone in attempting this sort of transformation,” notes Bloomberg. The story cites London’s new “Mini-Hollands” concept, which will deploy “Dutch planning ideas that seek to reduce or block car access to neighbourhood shopping hubs,” and Barcelona’s ongoing drive to turn “400-by-400-metre chunks of road in areas dominated by apartment towers into mostly car-free ‘superblocks’.”

But the path is easier for some to follow than others. “It’s one thing to turn a Paris or a Barcelona—cities that were almost completely shaped before the automobile was invented—into a neighbourhood-centric utopia,” writes Bloomberg. It’s quite another to transform the “younger, sprawling cities found in North America or Australia, where cars remain the dominant form of transit”—and where robust transit systems are not yet in place.

Working hard to “strike a balance between vision and reality” is Detroit, which, following the likes of Melbourne, simply added five minutes and embraced the “20-minute city” as its path to “vibrant vicinity.” Four years after Mayor Mike Duggan laid out a plan “to turn high-density corridors outside the central business district in his sprawling, 140-square-mile city into 20-minute neighbourhoods,” the city has implemented narrower streets to slow down traffic, wider sidewalks to accommodate cafés, better lighting, and “a US$17-million pedestrian upgrade in the Livernois-McNichols area,” with nine other districts in line for similar refurbishment.

But as laudable as these improvements may be, they have occurred in a city where “an estimated 30,000 citizens lack access to a full-service grocery store,” notes Bloomberg, citing a 2017 report by the Detroit Food Policy Council.

“We have to balance these targeted strategies with city-wide strategies that help everyone with their quality of life,” said Katy Trudeau, the city’s deputy director of planning and development. Part of Detroit’s plan to achieve just such a balance, she added, is a “new $50-million public-private affordable housing fund, which seeks to help low-income residents stay in place as property values rise in redeveloping neighbourhoods.”

But the 15-minute city concept is unlikely capture the imagination of Americans who already have a 15-minute reach to what they need—by high-speed freeway, that is. Adie Tomer, a fellow at Brookings’ Metropolitan Policy Program and author of the Food Policy Council report, told Bloomberg a revised, “three-mile city” concept might get more traction.

But whatever term is used, and wherever the concept of “vibrant vicinity” is deployed, city planners everywhere will have to tackle the problem of social equity—with affordable housing as the lynchpin of this ideal aspiration of a truly livable city.

“Many neighbourhood services rely on lower-income workers who often make long commutes, and a 15-minute city isn’t really one if only the well-off can stay put,” writes Bloomberg. So Paris is working to have “30% of its housing stock in the public domain by 2030, and it’s been increasing the share even in richer districts despite resistance from well-heeled neighbours.”