Tuesday, July 2, 2013

What is a peloton? Article in the Metchosin Muse

The following article of mine was published in the July/August issue of the Metchosin Muse (excuse the overlap). A more readable copy of the text follows (with a few minor edits from the printed version), following the article copy.


What is a peloton?
By Hugh Trenchard
Metchosin Muse  Vol. 21 Issue 7/8 (July/August 2013) p.13
photo and caption by Brian Domney

If you did not know what it was, from a distance and the right vantage point, it may appear as a gigantic amoeba that covers the width of the road, or like a snake that stretches 300 metres long.  Perhaps it is some unknown creature: it proceeds as an amorphous mass that shifts across the road, expanding and collapsing like an accordion. As it nears, whirring sounds and grunts are carried on the wind. Soon helmets may be discerned with the sun glinting off wheels and frames; then you may see spandex and turning legs, brown and muscled like horses.  This is not an alien creature at all, but a peloton, or a group of cyclists in a bicycle race. 
Every cyclist in the peloton races with some tactical or strategic objective in mind. However, at a more primitive level, each must be vigilant to avoid crashing into their neighbors, while keeping up speed with the group and adjusting their positions for the sweet spot where pedalling is easiest. If a cyclist shifts too far toward the back, she will know that the race is lost if she remains there until the finish, and so must constantly fight to stay near the front.
At this basic level, cyclists’ actions are determined by their responses to nearest neighbors, and by principles of physics, physiology and simple objectives.  Viewed this way, a peloton is very much akin to a flock of birds, or school of fish, or an ant colony. And for scientists who study them, animal collectives and biological and human systems like these are interesting because complex patterns emerge from simple underlying rules of behavior. 
In biological systems like these there are no leaders to command the positions of others within the group or how to go about their activities.  When patterns form without leaders, these patterns are said to self-organize, or to be "bottom-up" processes. In starling flocks we see amazing displays of self-organized shape and structure. On the West Coast we are all familiar with the precise, self-organized v-formations of geese. So too do we see similar structures and patterns in fish schools. In ant colonies, individual ants are not very smart, but sophisticated self-organized social behavior emerges when they interact according to a small set of basic rules. 
                A bicycle peloton is especially interesting because self-organized patterns emerge from basic human or physiological principles, while at the same time there are also leaders who may control the pace or command team-mates to alter their positions in the peloton. These leader-driven factors of bicycle racing are "top-down" in nature.
Self-organized peloton pattern formation is driven by three primary rules: avoid colliding with your neighbors, save energy by drafting (riding behind others), and advance toward the front.  We can see the first two of these are clearly universal principles, since we know how birds must avoid collision to stay aloft, and how their v-formations allow them to save energy and enhance their long-flight capabilities.
Some may argue that the third principle, the "front-position imperative" is not a universal biological principle, but is really the result of the competitive nature of a human-designed bicycle race and the objective of winning the race. However, we do actually see this kind of competitive drive in nature. For example, sperm engage in a similar competition for the front of the group and, as is commonly known, only one sperm will impregnate an egg.  Or, for a herd where food and water are scarce, the individuals who arrive at them first will survive, necessitating a competition for those resources. We can also imagine herds being chased by predators, where those individuals within the herd which advance to positions farthest from the predator are more likely to survive. 
                When we look at flocks, schools, or herds, it is not hard to see how they undergo changes in pattern formation. Some of these are changes in density, or how closely animals pack together. Some may be changes in alignment and direction, or speed. Changes in formation may be said to undergo phase changes, like those when water freezes to ice, or when water boils to steam.  It may seem obvious that this is what animals do, but the answers are not as obvious when you begin to explore why animals move collectively in the ways they do.
                Pelotons are accessible for studying all manner of collective behavior because we can obtain data about human physiological requirements, observe and track individuals who comprise the formations we see and correlate positional data with physiological data. Of course we can also learn from the riders themselves about their experiences. By contrast, it is not so easy to ask a goose how hard it was to keep up with the flock that brutish day in the howling headwind. But by learning about what cyclists do, so may we understand more about what starlings do, or what fish do, or what ants or huddling penguins do.
But the riches of peloton dynamics do not end there. There are other avenues of exploration as well. These studies fall within the domain of complex systems theory. Originally a branch of physics, it has grown in recent decades to be multi-disciplinary in scope, encompassing such disparate fields such as sociology, evolutionary biology, economics, ecology, and vehicle traffic flow.  By studying the amorphous oscillations of the peloton, we stand to gain insight into all of these areas.

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