World's Subways Share Common Mathematical Structure 159
Hugh Pickens writes "No two subway systems have the same design. New York City's haphazard rail system differs markedly from the highly organized Moscow Metro, or the tangled spaghetti of Tokyo's subway network. Now BBC reports that a study analyzing 14 subway networks around the world has discovered that the distribution of stations within each of the subway networks, as well as common proportions of the numbers of lines, stations, and total distances seem to converge over time to a similar structure regardless of where the networks were, when they were begun, or how quickly they reached their current layout. 'Although these (networks) might appear to be planned in some centralized manner, it is our contention here that subway systems like many other features of city systems evolve and self-organize themselves as the product of a stream of rational but usually uncoordinated decisions taking place through time,' write the study authors. The researchers uncovered three simple features that make subway system topologies similar all around the world. First, subway networks can be divided into a core and branches, like a spider with many legs. The 'core' typically sits beneath the city's center, and its stations usually form a ring shape. Second, the branches tend to be about twice as long as the width of the core. The wider the core, the longer the branches. Last, an average of 20 percent of the stations in the core link two or more subway lines, allowing people to make transfers. 'The apparent convergence towards a unique network shape in the temporal limit suggests the existence of dominant, universal mechanisms governing the evolution of these structures.'"
Slime Mold Grows Network Just Like Tokyo Subway (Score:4, Interesting)
http://www.wired.com/wiredscience/2010/01/slime-mold-grows-network-just-like-tokyo-rail-system/ .. old news?
Stockholm is an outlier? (Score:3, Interesting)
Re:Anyone know which subways they compared? (Score:5, Interesting)
Re:Chaos Theory (Score:5, Interesting)
Except it's not self-organisation. The stations don't dynamically shift around and lay new tracks according to their perception of traffic flow and population density; a dude sits down at a desk and draws it on a map.
Article is a barrowload of sensationalist monkey spunk.
Physics, not humans : slime (Score:5, Interesting)
Humans build systems to suit humans. The commonality is humans.
The commanity is physics and math; research on slime has shown that, when faced with the same constraints as the rail network, it will grow into almost exactly the same network structure. [bbc.co.uk]
Slime Design Mimics Tokyo's Rail System: Efficient Methods of a Slime Mold Could Inform Human Engineers [sciencedaily.com] "The model captures the basic dynamics of network adaptability through interaction of local rules, and produces networks with properties comparable to or better than those of real-world infrastructure networks... The work of Tero and colleagues provides a fascinating and convincing example that biologically inspired pure mathematical models can lead to completely new, highly efficient algorithms able to provide technical systems with essential features of living systems, for applications in such areas as computer science."
Re:Moscow Metro (Score:5, Interesting)
While this is a myth, another anecdote probably is no myth. The russian word for trainstation is vokzal. The word is not of russian origin, but english. When the first railroad was built in Russia, the 12 mile track between St. Peterburg and Tsarskoye Selo and further to Pavlovsk Palace, there were extensive pleasure gardens around Pavlovsk Palace, which were called vokzal (Vauxhall translated to russian letters) in the russian language - and got their name from the Vauxhall Pleasure Gardens in London. Thus the terminus at Pavlovsk Palace was called vokzal, giving raise to the generic russian word for terminus.