The “15-minute city” is getting some attention from urban planners.

The idea is that everyone should be able to access the key destinations in their day-to-day life–work, food, schools, recreation–within a 15-minute walk, bike ride, or mass transit ride of their residence. Cars would then be unnecessary for many daily tasks. Most Americans do not live with the experience of a 15-minute city: for example, the average commute to work, typically by car, is about 25 minutes each way. Here, I’ll sidestep the potential environmental or exercise-related benefits, and instead turn to an interview with Edward Glaeser by the McKinsey Global Institute (“What’s the future for cities in the post pandemic world?” April 17, 2024). When asked about the 15-minute city, Ed responds:

I do, in fact, have views on the 15-minute city. And I certainly applaud the idea that we’re going to have land-use regulations that are such that it’s easy to put residences, workplaces, cafés, and stores all in the same neighborhood. There are wonderful things about the 15-minute city, a vision of neighborhoods being full of lots of different amenities. It’s great. The ability for us to have access to lots of things without driving a car, that’s fantastic. But the view that we should basically see ourselves as being citizens of a sort of small neighborhood, rather than citizens of an entire metropolis, that feels deeply dangerous to me, especially in America, with its history of profound racial and income segregation.

Together with Carlo Ratti and a series of other coauthors, we put together a paper looking at, essentially, mobility using cellphones and the 15-minute city. And what we find in the US is actually the more that rich people, elites, live within their 15-minute area, they actually integrate more. So in an elite setting, it’s not a terrible thing. If you’re coming from a poorer area, if you’re an African American, the 15-minute-city experience is one that involves just much more experience segregation for them. And so if you want a city that’s integrated, you want to eschew the 15-minute city. You want to embrace a metropolis-wide vision of the city, not one that focuses on small little neighborhoods.

Glaeser always has interesting comments on the history of urban areas and where they are headed, and I recommend the interview as a whole. Here’s one other thought from him about how segregation within cities, by income and by race, varies between adults and children.

Residential segregation feels like it’s really important in lots of ways. And I think it is very important for children. Segregation has a very powerful effect in explaining differential outcomes for whites and African American kids. But as recent work using cellphone data, by Susan Athey and Matthew Gentzkow and their coauthors have shown, experience segregation for adults can be very different than residential segregation.

In most American cities, you get up in the morning, you leave your segregated neighborhood. You go to an integrated firm. You interact with lots of different people. And so the neighborhood doesn’t matter. But it does matter for kids. Because the kids actually don’t go to work in an integrated company. They go to a segregated school. They play on a segregated street corner. Understanding this feels important to me. I have new work with Cody Cook and Lindsey Currier that tries to differentially look at them, the cellphone mobility patterns of poor kids and rich kids, and just documents how much more of a life that is disconnected from the marvels of urban areas that the kids of poverty experience, even in wealthy cities.

Of course, Glaeser’s argument is not a dispositive or unanswerable argument against the idea of a 15-minute city. But it can be a thin line between the idea that it would be nice if more people could aim to work and carry of many aspects of day-to-day living in walkable neighborhoods around our residences, and the argument that people really should mostly stay in their own 15-minute zones, rather than mixing more widely across our urban areas.