Motorcycle Boids or “Safety in Flocking”

When we strike out on our rally rides to places like Devil’s Tower, Sundance, Custer State Park, the Badlands, Wind Cave National Park, Hot Springs, Mammoth Site, Mount Rushmore and a hundred other attractions there is no accounting for why you see hundreds of bikers riding together in one direction and hundreds more riding together in the opposite direction.

Many times I have “joined” a group seemingly travelling together when, without formal notice, a smaller fraction breaks off while the rest of us continue along our shared path. Even though we don’t have a common destination we flock together naturally for the period we do a have a common path.

I’d love to study the traffic patterns of all these thousands of bikers over the course of the week. I imagine the patterns would display like multiple flocks of birds or schools of fish all going in different directions together using each individual’s basic sensory and steering mechanisms of separation, alignment, and cohesion.

Each boid has direct access to the whole scene’s geometric description, but flocking requires that it reacts only to flockmates within a certain small neighborhood around itself. The neighborhood is characterized by a distance (measured from the center of the boid) and an angle, measured from the boid’s direction of flight. Flockmates outside this local neighborhood are ignored. The neighborhood could be considered a model of limited perception (as by fish in murky water) but it is probably more correct to think of it as defining the region in which flockmates influence a boids steering. *1

Good riders either have learnt these basics or have a natural sense for flocking but this is what makes a rally ride relatively safe. You want to belong to the group of individuals going in a generally agreed upon direction, you want to follow the basic flow (direction and speed) of the group, but you don’t want to get too close. Statistically the more the riders the safer the ride. Even less experienced riders can sense the flow and as long as the flow doesn’t exceed their individual motor-skills then they will stay safe by following the flow. The group also has to sense the overall ability of the individuals so that they don’t collectively over-ride the situation.

Individualistic Behavior
It’s the few that “don’t get it”, either by being too slow or by being too fast (in speed or reaction time), that cause accidents or have accidents. This 2011 rally year there were two fatalities both from a rider or driver not following the flow.

A 70-year-old Missouri man became the first fatality of the Sturgis motorcycle rally in western South Dakota Tuesday. Peter Diangi of Sunrise Beach, Mo., apparently lost control of his 2003 Harley Davidson Road King on a downhill curve about five miles south of Deadwood around noon Tuesday, according to Sgt. Rick Miller of the South Dakota Highway Patrol. Diangi’s motorcycle was traveling at a high rate of speed. He was thrown from the vehicle when it slid into the ditch, according to Miller. Diangi was not wearing a helmet. *2

In an unrelated accident a rider was hit by a negligent car driver. The biker was riding safely within a group going in the same direction and at the same speed. The car driver was weaving in and out of traffic going much faster than the flow and hit the motorcycle from behind pushing him into the ditch. The rider was thrown off his motorcycle. He was not wearing a helmet and immediate cause of death could not be determined.

Throughout evolution we have learned that our safety depends on sticking together and creating a “safety in numbers” situation like I do when I join another group of riders. (I have even inadvertently on different occasions joined a gang of Satan’s Choice and Hell’s Riders without any objection on their part.) Regardless, we still have this stubborn individualistic streak which is associated by many Harley riders with the concept of Freedom. Freedom is not associated with the right to choose but rather with the individual’s right NOT to wear a helmet. The expression of Freedom cannot be manifest if one chooses to wear a helmet.

I actually had a very sensible owner of a successful real estate business tell me that he rode a Harley up until his state passed the mandatory helmet law. He has never ridden since. He asked me, “What is the fun of riding a motorcycle if you have to wear a helmet?” My first reaction is to say “If you have to ask that question then you were riding for the wrong reasons,” but statistically speaking if there were many bikers who wouldn’t ride because they had to wear a helmet then riding would be less safe even for riders like me who do wear a helmet because there are less bikers on the road.

I believe that particular piece of theoretical statistics from experience because the closer you get to Sturgis, especially during the rally, the more likely the car and truck drivers are to see and accommodate the motorcycles. The further you move away from Sturgis the more dangerous the drivers become. In fact, I believe the most dangerous day of riding is the day you get back outside the 100 mile safety radius from Sturgis because you have become acclimatized to the extra attentive drivers in South Dakota.

That does not mean that SD drivers are more attentive to bikers, although they may be, but considering that SD has an enormous influx of summer tourists who have not come for the rally but who quickly become acclimatized to the large number of bikers means that they are adapting to the number of motorcycles rather than the motorcycles. This is an example of “safety in numbers” in action.

The other example is the fact that most Harley riders are not highly experienced riders. Most of them bring their bikes to the rally on the back of their Harley-Davidson series Ford 250 trucks or in special motorcycle trailers. These guys don’t wander any further then they can comfortably ride out and back in one day from Sturgis and they always go in groups or flocks. This is so common a practice that the select few who ride their bikes to the rally actually have bragging rights to say “I rode mine.”

Another notable statistic is the amount of riders who mysteriously drift off the highway and die doing so. These are inevitably the lone riders. I know when I ride in a pack I stay awake and attentive at all times. There is no drifting off.

Relatively, however, these weekend riders are safe as long as they don’t go outside their “safety in numbers” zone. In other words, stay with the group and don’t go far from Sturgis. So what does that mean for the rest of us long distance experienced riders?

In 8 out of the 9 fatalities cited in the accident report I got these cases from the riders were not wearing helmets and I believe many would have survived, often without further injuries, if they had just worn an approved pot on their heads. But if everyone wears a helmet are we all safer? I am betting that I am safer because I wear a helmet and they don’t. The safety in numbers keeps them safe and the combination of my driving experience, maximizing the safety in numbers approach when able, and, if that fails, my helmet keeps me safe. Thanks Harley for contributing to my safety.

I just want to cite one more accident also from this year.

One man is dead after a motorcycle wreck on Interstate 90 near Wasta Wednesday evening at 5:30 p.m. Kurt Lee Stolba, 57, if Wilton, Ia., was traveling eastbound in I-90 on a 2008 Harley Davidson motorcycle. Witnesses reported that a bolt of lightning struck the rider. *2

OK, sometimes shit happens!

See you in Sturgis next year. Ride safe.

For all images of our visit to Sturgis 2011 visit Travelographer

2011 08 Sturgis Rally

*1 Boids
*2 For those who were lost.
More on the hit and run accident on a site ironically called Chaos Nation


About John S Goulet

Air Transport Pilot, consultant, writer, blogger and photographer with 40 years in Professional Aviation.
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