Global subway systems converge on common topologies


35 Responses to “Global subway systems converge on common topologies”

  1. digi_owl says:

    i suspect we will see the same if we observe roads over time.

    • James B says:

      I think I learned somewhere that there are emergent patterns in road development as well.  Something about how prior to the automobile, cities grew in spokes along rail lines and waterways.  Then with cars and roads, you started to see concentric rings of growth rather than fattening spokes.

  2. Heartfruit says:

    Except in Toronto where we argue over subway plans for 20 years and then don’t build them

    • Kyle Mosley says:

      nonono, first you build a new subway line to an Ikea.  Then, years later it is determined that one of Canada’s largest universities should maybe have subway access too.  But most importantly, Ikea gets the access first.

  3. totally80s says:

    It would make similar sense to say that most cross country rail systems worldwide adhere to “a common topology” – cross country track is generally stretched out straight over wide gently rolling swaths of landscape.

    Instead of saying that subways have global similarities, it makes more sense to say that large cities themselves adhere to a common topology. Generally speaking, London looks like Los Angeles looks like Tokyo. Their transit systems just happen to look nearly alike, because they ARE nearly alike.

    • Jesseham says:

      Yeah, I was thinking along the same lines. Cities have suburbs.

      • JonS says:

        Even from just the snippet it’s a bit deeper than “cities have suburbs”. The form factor of the subway net (circle and spoke vs grid) abd especially the ratio of the inner to outer net are both – to me, at least - non-obvious things to be the same across multiple cities.

        • twianto says:

          A grid is your layout of choice if you desire minimum efficiency. Not terribly surprising that this isn’t what most cities choose.

        • As @twianto:disqus said, the reason we don’t use a grid is because it would be horribly inefficient; unless people only go up and down and left and right.

          This is the layout that’s used because it’s the one that makes sense.

          Glad I’m not the only one who thought this all seemed a bit obvious.

    • Cities and railway systems spread like slime-mold.

    • hadlockk says:

      I wonder if they look alike because they were built by the same people. You don’t just look at London’s underground system and say, “hey, that’s neat, let’s have a go at it.”. No, you hire the people who built London’s (they’re out of work, right? there’s only so much subway a city can afford each decade) and have them plan it out for you, then subcontract it out to your local construction industry. Cut copy paste. This isn’t like the space race, where you had two independent systems with almost no sharing of information.

      • twianto says:


        (I certainly hope that the people who built the London Underground in the late 1800s don’t have to work anymore.)

        • AlexG55 says:

          Not to mention that the systems are often built over decades if not centuries. I mean, I imagine that the people who built the Jubilee Line Extension are still working- probably digging Crossrail. I agree that all of the builders of the original Underground are, well, underground by now.

  4. Matt Blind says:

    “And so, by 2024, the impact of his noodly appendage was visible in every city in the land; the FSM Subway Map Gospels”

  5. pjcamp says:

    “Subway systems seem to gravitate towards these ratios organically, through a combination of planning, expedience, circumstance and socioeconomic fluctuation, say the researchers.”

    And, here in Atlanta, fear of black people.

    • James B says:

       I remember when they built and operated the first MARTA train.  I think it was all buses before that.

      • pjcamp says:

        It’s still a lot of buses. And in particular, suburban Cobb and Gwinnett counties both run their own bus lines whose sole purpose is to transport people from those counties to a MARTA station. MARTA has proposed extending the trains up into those counties on several occasions and the county governments have opposed it out of fear of crime (= fear of black people). By having separate systems with a restricted set of linkages, they believe they can more easily control the flow of criminals/black people into their counties. As if someone is going to take a three hour train ride to steal a TV and transport it back on the train. To this day, the only places where the train lines cross I-285 is where they can stay inside Fulton or Dekalb counties.

        And Republicans think racism is no longer a problem (except against white people).

        • James B says:

          Yeah, I see that “what about racism towards white people?” line coming up quite a bit since that thing in Florida.  You think guys born into the most privileged group on earth would somehow appreciate it more.  But maybe, as the distribution of race in American society continues to shift,  they might live long enough to actually get a well deserved taste of it. 

          And that is interesting about how those attitudes effect MARTA routes.  I suspect some people out in those suburbs like having a car as a ‘barrier to entry’ for living there.

  6. Shashwath T.R. says:

    Forget the paywall – the paper’s on arxiv:

  7. timquinn says:

    Look at my paper. I did a study and found that the words mean exactly what I said they meant when I designed the study. Statistics verify it.

  8. awjt says:

    It all looks like His noodly appendage to me… 

    oops Matt beat me to it

  9. Douglas Stuart says:

    Well, at least the image is somewhat misleading, as the MAPS do look similar, but the maps are designed to convey routing information, not topological or pure geographic information.

  10. tomrigid says:

    I suspect that the physical layouts exhibit even greater self-similarity than the maps; no human being would stack books like that.

  11. Oliver Crosby says:

     Looks like you can download this article for free from Cornell:

  12. uh can someone say selection bias?

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