Joel recently noted an academic study that suggests subway systems converge on a similar form. Whet Moser of Chicago argues that understanding subway patterns requires considering how cities grow and the concentric rings model of the Chicago School of urban sociology.
This is where I get skeptical that subways converging towards a “common mathematical space may hint at universal principles of human self-organization.” The subway systems the authors study were built within a relatively narrow band: 1863 (London) to 1995 (Shanghai). But they’re all also very old cities. Shanghai has a dense central business district, dating back to its long history as a port town; Moscow’s rings radiate out from the Kremlin and Red Square, following old fortifications; Beijing grew out from a model of urbanism that way predates Burgess and Park:
Many researchers reached consensus on urban morphology of the Old Beijing from physical composition. It is agreed that the Old Beijing was laid out exactly according to the concept of the Chinese utopia capital city in the book Kao Gong Ji, Notes on Works, written more than 2,000 years ago. The ideal city form is ‘a walled square city of nine by nine li (4.5 kilometers) with nine north/south main streets and east/west main avenues, three gates on each side, the ancestral temple on the left and an altar on the right of the palace, municipal administration buildings in front of the palace and a marketplace behind it’ (Fu, 1998; Liu, 1986).
So: who cares? If it’s just a neat little mathematical model, what’s its relevance? It’s relevant when the model becomes prescriptive, as the authors of “World Subway Networks” write:
In the case of Beijing, Seoul and Shanghai, it seems that their relative ‘youth’ is why they have not yet reached their long time limit.
Translation: since the subways were started after 1971, they haven’t fully converged on that ideal “core and branch” shape and ratio…
In short, Beijing is stuck in Park and Burgess’s concentric zones, and wants to move towards Harris and Ullman’s multiple-nuclei model. At the very least, it’s neat to see these comparatively dated theories of urbanization at the forefront of 21st century development. But the Beijing subway system may be following a multiple-nuclei model…
In other words, urban sociologists started to figure out that the concentric rings model doesn’t seem to fit all cities (though it still seems to overlay nicely on Chicago, it doesn’t fit other places like Beijing or newer Sunbelt cities in the United States). First came the multiple nuclei model in the 1940s and then a whole new paradigm, the political economy approach, started to emerge in the 1960s. The political economy prescriptive relies less on prescriptive models and instead focus on a different mechanism: whereas the Chicago School emphasizes competition for land and cities growing as people seek out cheaper land, the political economy model focuses on the profit motives of developers, politicians, and business leaders.
So if we looked at subway growth and locations in the political economy perspective, we could examine why lines and stops were built in certain places. Using two other forms of mass transportation as examples, we know that a good number of railroad and streetcar owners in the mid to late 1800s built lines to their new real estate developments. In other words, these lines were not built to service existing residents but rather to spur new development. I bet you could find some scholars who would argue that subways may sometimes be built to wealthier neighborhoods rather than poorer neighborhoods because there is more money to be made in these connections.