Are Transportation Planners Smarter Than Mold?

Transportation planners are a noble and advanced species; all I have met have opposable thumbs, walk upright, and have a reasonable command of fire and language. But the results of a fascinating new experiment reported in the journal Science give us cause to question whether their work would be better performed by primordial slime.

A team of researchers led by Atsushi Tero simulated how Tokyo’s rail system would have developed if slime mold was calling the shots. See the original paper if you have a subscription to Science (warning: lots of advanced math) or this helpful summary by MSNBC, which brought the story to my attention.

To make a long story short, slime mold is a unicellular organism resembling a fungus. As it grows, it oozes outward seeking out food sources, then it connects these by forming narrow veins that look suspiciously like transportation links. For economy’s sake, the mold forms the most lean and efficient network possible while maximizing its access to nutrients.

The scientists placed food deposits (oat flakes) in a pattern that mimicked the distribution of population in the greater Tokyo area. They also discouraged mold growth in areas corresponding to obstacles like ocean and mountains by placing light sources (mold’s sworn enemy) in these spots. The researchers then introduced a single deposit of the mold on their mock central Tokyo and let the slime do its thing.

The result? The mold formed a network that closely mimicked the actual Tokyo railway map. In terms of efficiency and fault tolerance, the mold performed about the same as the real Tokyo system, and it did so at a slightly lower cost. All of this was done without any guiding overall intelligence, but through a decentralized method in the mold that continually adapted to reinforce links that performed well, while eliminating those did not.

What’s the lesson here? There is no question that, by its nature, surface transportation requires considerable planning by government. For example, the land for rights-of-way can generally only be assembled using the power of eminent domain.

But given some of the disappointing results of top-down transportation planning, on both the road and transit sides of the coin, perhaps it’s time that we consider introducing more bottom-up, organic planning into the system.

How might this be done? Consider the possibilities opened up by variable-rate electronic road tolling. I sang the praises of such a system, in terms of congestion reduction and revenue generation, here and here.

But one benefit I didn’t mention is that tolls will provide market signals about the demand for transportation resources. If demand on a road is high, the tolls will rise, which will indicate that it may be time for additional investment in a corridor. Since the financial benefits of new investment can be recaptured thanks to tolling, high demand should attract the appropriate resources, whether public or private. (Capacity expansion might come in the form of increased express bus service in the tolled lanes, transportation management measures like roving service patrols, or new infrastructure like grade separations, double-decking and tunneling.)

Sound suspiciously like creeping capitalism? Perhaps. I’m not advocating a wholesale privatization of our road system. Market forces never totally eliminate the need for central regulation and planning. But at the same time, the supply-and-demand system works pretty well in the way it allocates resources throughout the rest of the economy.

Organic development can complement the planning efforts of a central intelligence. Planners see the big picture, but may have limited information about the small details. Organic planning accumulates the collective wisdom of myriad individuals who each know only a very small part of the picture, but know their part very well. Tolling could help us come up with a system that maximizes the benefits of each approach.

There are definitely times when having a central nervous system comes in handy; I make use of mine quite frequently. But maybe sometimes it’s best to get back to our evolutionary roots and act like slime.

(HT: Kevin Morris)