A popular new study claims to lump cities into four types. But the real science of cities is heading toward a more complex understanding of how

In the so-called “science of cities,” we may be approaching a moment where mere classification of city types—a long tradition in urban studies—and vague, untested hypotheses are moving toward a more unshakable model or how cities evolve.

Take, for example, a headline from a couple of weeks ago. Gizmodo, Popular Mechanics, Atlas Obscura, Motherboard, and Discovery announced that there are only four kinds of cities in the world—apparently, a new mode of classification for cities.

The study described in these articles goes something like this: Using data mostly from OpenStreetMap, French theoretical physicists Marc Barthelemy and Rémi Louf measured the size and shape of land blocks in 131 global cities, ... 

Rémi Louf1⇑ and Marc Barthelemy1,2⇑

Author Affiliations

  1. Institut de Physique Théorique, CEA, CNRS-URA 2306, Gif-sur-Yvette 91191, France
  2. Centre d'Analyse et de Mathématique Sociales, (CNRS/EHESS) 190–198, Avenue de France, 75244 Paris Cedex 13, FranceAbstract

We propose a quantitative method to classify cities according to their street pattern. We use the conditional probability distribution of shape factor of blocks with a given area and define what could constitute the ‘fingerprint’ of a city. Using a simple hierarchical clustering method, these fingerprints can then serve as a basis for a typology of cities. We apply this method to a set of 131 cities in the world, and at an intermediate level of the dendrogram, we observe four large families of cities characterized by different abundances of blocks of a certain area and shape. At a lower level of the classification, we find that most European cities and American cities in our sample fall in their own sub-category, highlighting quantitatively the differences between the typical layouts of cities in both regions. We also show with the example of New York and its different boroughs, that the fingerprint of a city can be seen as the sum of the ones characterizing the different neighbourhoods inside a city. This method provides a quantitative comparison of urban street patterns,1 which could be helpful for a better understanding of the causes and mechanisms behind their distinct shapes.

  • 1. According to their findings, across the globe and throughout history, these characteristics grow predictably along with city population; in other words, cities "scale" in astonishingly predictable ways. The next step for Bettencourt and West is to develop a mathematical description that successfully predicts what creates these scaling patterns.

    And that is where Barthelemy and Louf—they of the city block classifications— eventually see their research going, even as plainly morphological as their first findings are. Eventually, says Barthelemy, "we want to disentangle all thedifferent factors that shape a city, and try to understand what the main mechanism."

    So are we getting closer to an evolutionary theory of cities? Can there be a grand, unified law of how cities grow, scale, and shape-shift to hang all of urban studies upon? Perhaps—though some of the strongest proponents of the “quantifiable city” aren't sure.

    “Maybe there’s some unequivocal explanation out there," says Michael Batty, author of The New Science of Cities, which lays out mathematical models designed to predict human interactions and resource flows in cities. "But I tend to think that’s almost impossible, given how cities are made of individuals. Maybe we’d have some measurements that will be stable for a time, but they’d be bound to change eventually.”

    Maybe. Or maybe the science of cities is still in its pre-Darwin days: a juvenile field, with systems of classification and shaky theories of evolution growing towards something great.