Today we've got a guest column from Temple University medical student Carl Beyer. In the course of his research, Carl came across some interesting articles concerning the organic growth of nutrient transportation among a colony of mold and how the natural processes can be related to the "organic" growth of human transportation networks. Just goes to show you that you can learn some unexpected things from nature, even the mold growing in those dishes you haven't washed for two weeks.
In the competitive world of microorganisms, inefficiency is often punished by extinction. A method for incorporating the same ruthless efficiency into the development of infrastructure networks could be quite valuable. A research team led by Atsushi Tero has developed an algorithm that may do just that by comparing the growth of slime mold to the train network of Tokyo.
These researchers studied the slime mold Physarum polycephalum which develops a transportation network of small tubes for carrying nutrients and waste products. The mold expands outward looking for new food sources and connects these scattered nutrients to the central network by adding and subtracting tubes. The researchers used a clever set of experimental protocols to make the mold's environment simulate the population density and geography of Japan. Nutrient clusters were used to represent population centers and bright lights, slime mold's deadly enemy, were used to mimic geographic limitations like mountains and oceans. The result was that slime mold grew a transportation network very similar to the real train network connecting Tokyo and neighboring cities. This result is amazing because the slime mold was able to create an efficient transportation network with no central planning and at a slightly reduced cost. Atsushi Tero and his team showed that it can achieve this efficiency because each tube either grows or shrinks based on the level of protoplasm (slime juice) flow through that particular tube.
So how can this biological algorithm be put to use in the real world? The flow of people, goods, or information is equivalent to the flow of protoplasm and our human networks can be tuned to respond in the same manner as the slime mold tubes. To continue the train example, a particular rail line could respond by increasing the length of trains, frequency of trains, layout of train cars, etc. as a way to "expand the tube". The same is true for highways where additional lanes could be added, lanes could be reversed during certain times, and busing and carpooling could be expanded. Most governments and transportation companies already factor levels of use into their future plans, but this organic framework provides a naturally proven mathematical algorithm. The one catch to using this sophisticated planning tool is that segmental data for each stretch of highway or railway is needed to provide an accurate model. The electronic tracking of train tickets both on and off of a train could be an easy method for data gathering, but an equally effective method is not readily apparent to me for roads.
In conclusion, some central planning will always be important for infrastructure to provide the political will to build such expensive public goods, but the actual design of the network may be better left to slime mold.
Sources:
Rules for Biologically Inspired Adaptive Network Design, Tero et al. Science; January 22, 2010.
http://www.msnbc.msn.com/id/34980542/ns/technology_and_science-science/
http://freakonomics.blogs.nytimes.com/2010/02/02/are-transportation-planners-smarter-than-mold/
http://www.msnbc.msn.com/id/
http://freakonomics.blogs.
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