Rules of Interaction & Urban Flow

Birds in Romephoto source

Los Angeles. Palm trees, movie stars, swimming pools, smog, and traffic. Spend much time in L.A. and you’ll likely spend as much time in traffic as you do eating and exercising combined. I made up that pseudo-statistic, but that doesn’t make it untrue. Enough people spend enough time in traffic in Los Angeles that a sort of social evolution occurs. Looking down from an overpass one witnesses a sort of miracle: millions of cars weaving across six or eight lanes at varying speeds, somehow maintaining a nearly universal distance from each other, avoiding collisions, with practically no direct communication and absolutely zero planning or leadership. A mechanical herd of caribou, a gas-powered flock of birds.

The flow is far from perfect. Accidents do happen, bottlenecks are commonplace, speeds are often lower than desired. But it’s there. It’s visible. Perhaps not on par with the avian ballet of Winged Migration, but the behavior of drivers in heavy traffic (particularly when they are accustomed to heavy traffic) is noticeably different than the behavior of drivers in light traffic. When freedom of movement gets restricted by the phalanx of fellow motorists a strange sort of surface tension develops, like drops of rain coalescing into a stream.

Many of us have seen a bird fly into a window (a carrier pigeon actually crashed into my porch door earlier this week). But how often do you hear of an entire flock knocking themselves stupid? In the book Getting to Maybe, the authors reference the research of Craig Reynolds, who developed computer simulations in order to understand why “a flock of birds, a school of fish, or a hive of bees is up to fifty times more sensitive to changes in its environment than any single bird, fish, or bee.” A common notion is that flocks of birds take their cues from a lead bird, but if the lead bird in a flock crashes into a building those behind him simply fan out and reform once past the obstruction, like water flowing around a rock.

Reynolds recognized the improbability of the heroic leader bird theory and disregarded it, focusing instead on rules of interaction that would increase sensitivity to stimuli and environmental changes. Different sets of rules would cause his digital “boids” to move in different patterns, and through trial and error Reynolds discovered three simple rules of interaction that made his boids fly just like birds.

1) Maintain a minimum distance with other boids and objects

2) Maintain the same speed as neighboring boids

3) Move toward the center of the flock

In order for the simulation to accurately replicate birds in flight, all three rules must be continuously in operation. If any one of them is ignored, disaster ensues. Think about that for a moment. Three simple immutable rules, simple enough for birds with their teeny tiny brains to follow, enable a flock of thousands to move rapidly and without incident, reacting instantly and nimbly to any obstacle along the way. Makes the L.A. freeway miracle rather mundane, doesn’t it?

Of course, birds, fish, and bees aren’t chirping on their cell phones. They’re not texting, reaching for their coffee, or reading a newspaper (I’ve actually seen this on the 405 several times, newspaper spread out across the steering wheel, the driving catching up on the funnies at 70 mph). So is it merely a matter of paying attention? I don’t think so, at least not entirely. Paying attention is critical, but I doubt birds are consciously analytical.

Tokyo’s Shibuya district and its iconic and enormous crosswalk is famously crowded. While crossing it in the midst of a thousand-strong throng of pedestrians a couple years ago I felt oddly calm and uncrowded, almost as if I was crossing alone. I knew that I wasn’t going to run into anyone and that no one was going to run into me. We just flowed past each other. In Beijing or Shanghai you see a madhouse of pedestrians, cyclists, rickshaws, cars, delivery trucks, all enmeshed in what to Western eyes seems like chaos, and yet somehow still flowing. They are being like water, as Bruce Lee famously advised.

The authors of Getting to Maybe describe what happens whey you ask human beings to follow Reynolds’s three rules of interaction:

In a large space, ask each group member to do three things: (1) find two ‘reference’ people whom she will secretly keep in her sights for the next few minutes, (2) begin and keep moving around the space without bumping into anyone else, and (3) try to stay equidistant from the two reference people. As everyone does this, someone watching from a balcony above will see a pattern reminiscent of flocking birds, although the people involved may not be aware of the pattern.

Even more interesting, now pick two people and tell them quietly that, while continuing to keep equidistant from their reference people, they should gradually move toward and out the door. In as little as sixty seconds the entire group will have swarmed out of the room.”

In any major city it’s easy to spot the tourist: he’s looking up at the buildings as he walks. The locals, naturally, are looking straight ahead. Their attention is diffuse, their peripheral vision expansive. They are flowing. They are birds in flight. The tourist might stop abruptly to take a picture or gawk at a sight and trigger a chain reaction of escape maneuvers throughout the crowd behind him. Part of being urbane is accepting that public space is shared space, that when in public you are constantly interacting with other human beings whether or not a word is spoken, that rules of interaction are different than rules of isolation.

The United States, like the rest of the world, is rapidly urbanizing. But urbanity is more than density, more than skyscrapers and traffic and twenty-four-hour smoothie joints. Urbane behavior is characterized by the reconciliation of me and we: each has its time and place. It requires a heightened sensitivity to changes in the surrounding environment, and that takes time to develop. But what if we taught drivers to be more like water? Or birds? What if we extended the education to cyclists and pedestrians? Why not teach urbanity as well as urbanism?

I’m not saying Bret Easton Ellis is wrong; people in Los Angeles may well be afraid to merge. But they do it anyhow, albeit in fits and starts. Like the Japanese in Shibuya and the Chinese on the streets of Shanghai they subconsciously imitate birds, fish, cattle, and bees. Paradoxically, by imitating animals they assert their humanity; urbane behavior is a choice, the apotheosis of free will. So. The next time you drive someplace, consider the fact that every action you take follows a choice you made. Choose to fly like a bird and traffic might just become a whole lot less frustrating.

This entry was posted in Josh Grigsby, Rants, Response Pieces, Transportation, Uncategorized, What if?. Bookmark the permalink.

2 Responses to Rules of Interaction & Urban Flow

  1. faslanyc says:

    Interesting! For me car/pedestrian traffic is interesting to think of in terms of emergent behavior and phase-changes. Seed Magazine had a really cool article a few months ago on this very thing:
    Also, the quote you have of Reynolds’ exactly describes emergent behavior. But it only exists within parameters, right? And too little density, or too much (like a traffic jam) and the dynamic breaks down. So for urban planners there have to be contingencies that provide for both too little and too much, right? What do you do once a system crosses a “threshold” and the pattern breaks down??

    • josh grigsby says:

      Certainly, I think planners need to consider what the parameters are and how to deal with situations that fall outside them. But (and I’m writing as I’m thinking here) there may well be a natural equilibrium achieved when systems of balance are employed. Economies built solely around efficiency, for example, are inherently unbalanced because they only favor the most efficient producers. Systems of transportation become unbalanced (and flow is stymied) when one mode is favored at the exclusion (or at least to the detriment) of other modes. I think if the core systems are structured for balance, then the parameters will in large part take care of themselves. In general, I think too much attention is lavished on band-aids (i.e. how to create more affordable housing), and too little on reshaping the system that created the imbalance in the first place (how to negate the need for affordable housing).

      That said, there is also a human scale component that Reynolds’ work points to…a flock of birds functions the way it does not because it is governed by a system, but because each bird in some way chooses to participate in that system. What if planners were also educators? Consciousness-raising can be every bit as powerful as systems reform, and it seems logical that the two should be undertaken in concert.

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