World’s Subways Converging on Ideal Form

by Christopher Paul on May 16, 2012

Anthropology and sociology are the non-computer and non-business/economic sciences that fascinate me more than anything else. If I hadn’t gone into the business and computer industries, I probably would have studied one of those two fields (or psychology). So it’s especially interesting to me when I read about how Subways, over time, have converged to like organizational structures and designs.

With equations used to study two-dimensional spatial networks, the class of network to which subways belong, the researchers turned stations and lines to a mathematics of nodes and branches. They repeated their analyses with data from each decade of a subway system’s history, and looked for underlying trends.

Patterns emerged: The core-and-branch topology, of course, and patterns more fine-grained. Roughly half the stations in any subway will be found on its outer branches rather than the core. The distance from a city’s center to its farthest terminus station is twice the diameter of the subway system’s core. This happens again and again.

Looking at a graph they produced, you can see the ration of branch stations to core stations have moved towards a common range. It’s fascinating for a few reasons. It shows that humans think and organize in similar ways because many of these systems were designed independently. But it’s also an interesting study in how city planners react to population changes or how populations react to planning. I’d also argue it’s a fascinating study in how cities limited resources with the needs of the many over the needs of the few.

This is so interesting to me. I’m looking forward to followup observations.

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