Fifteen-minute cities are about convenience, not conspiracy

The writer is a professor at MIT, where he directs the Senseable City Lab, and a co-founder of CRA — Carlo Ratti Associati

Not that long ago, the 15-minute city was a clever urban planning theory to make neighbourhoods walkable, and the UK prime minister Rishi Sunak was an evidence-led technocrat who could make the Conservative party viable. More recently, however, conspiracy theorists have branded the 15-minute city a secret scheme to take away our cars and trap people in ghettos, and Sunak’s cabinet is even flirting with these ideas. What has been missing from this debate? Evidence.  

Our latest study at MIT uses US mobility data to quantify 15-minute cities, discovering how they affect human life and how they come into existence: the answer is deregulation, not government action. If Sunak is so serious about data, he should take a moment — perhaps 15 minutes? — to look at some. 

The concept of a 15-minute city emerged in the second half of the 20th century as an alternative to modernist single-use zoning, which separates homes, offices and retail into discrete areas. Imagine replacing this with mixed-use neighbourhoods, where offices, schools, shops and parks are all within a 15-minute walk or bike ride from your home. Food deserts and dead neighbourhoods would turn into lively communities, reducing long commutes. 

This paradigm — championed since 2016 by French urbanist Carlos Moreno — gained traction for a while, until the conspiracy theorists got their hands on it. Alt-right influencers seized on the 15-minute city earlier this year as an undercover plan to restrict car use and trap people within a tiny district. The accusations are wild, but have gained traction all over the world, and particularly in the UK. Fears — like those which flared on the streets of Oxford — risk contaminating our understanding of what the 15-minute city really is. 

In our study, we used anonymised cell phone location data for 40mn Americans to measure how often residents within one neighbourhood carried out essential trips within a quarter-hour timeframe. The results showed that people automatically construct their lifestyles around 15-minute walks if amenities such as parks and grocery stores are available within that radius. In other words, if we build it, they will come.

Part of our study focused on New York, where a 1961 zoning code, looser in some neighbourhoods than others, created ideal conditions for a natural experiment. The findings were striking: if the city permitted more commercial development, 15-minute amenities would naturally emerge. So we can see that 15-minute cities historically arose from deregulation: since people like having short commutes and enjoy interesting neighbourhoods, free markets create them.  

However, we also found a real downside to the 15-minute city and one that its supporters should pay attention to: greater segregation. Residents of poor neighbourhoods, if they only visit nearby places, are less likely to encounter economic diversity. This is of grave concern because economic success depends on residents’ ability to travel across the city and find new opportunities. As our co-author, Harvard professor Edward Glaeser, writes: “I am very worried that a focus on enabling upper-middle-income people to walk around in their nice little 15-minute neighbourhood precludes the far larger issue” — improving mobility for those in poorer areas.  

This is not to say that close amenities are intrinsically bad for lower-income people: on the contrary, they’re vital. But the 15-minute city must be paired with investment in transport between neighbourhoods. That means neither cycle paths nor roads for the motorists Sunak has decided to champion, but unglamorous, affordable buses and metros. 

Of course, it is unlikely that these findings will dispel the conspiracies. Handling such nuanced issues, and telling the truth about them, is the responsibility of serious political leaders. If Sunak aspires to be one of them, he should return to the hard facts.