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Old June 16th, 2010   #1
Randoman
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Default Motion Camouflage and the Looming Effect

Below is a cross post from another list. It's about left turns into the paths of m/c riders. How they happen and some suggested techniques to reduce the chance of becoming a statistic. Motion Camouflage and the Looming Effect were new terms to me for what I intuitively know to be fact. Hope it helps others on the list avoid both.

Rando


One of the most uncomfortable things I encounter while riding is wondering if that car ahead is going to turn left in front of me. Another is people running through the stop sign as they come off the freeway.

Here's couple of posts from my local forum that explains very well why the left turners might not see you.

Most crashes between a motorcycle and a left-turning vehicle are preventable. And many can be prevented easily by maintaining speed consistent with the traffic environment.
The Truth About Left-Turn Crashes
While a crash between a motorcycle and a left-turning car is almost always assumed to be the fault of the driver, the truth is that many (though not most) are caused by the rider. Of 159 fatal motorcycle crashes in the Bay Area in 2006-2007, 33 involved a car crossing the motorcycle's path, usually a left-turner, either oncoming or from a side street. Of those 33 crossing-vehicle crashes, 17 were caused by the driver, 14 by the rider, and 2 are undetermined. Among the 14 caused by the motorcyclist, the rider ran a red light or stop sign in 7 of them, and in the remaining 7 excessive speed was cited as the cause, with speed from 15 to 35mph over the limit reported. It's pretty obvious how running a red light can cause a crash, but the contribution of speed can be more subtle.

How Speed Contributes

At high speed a motorcycle becomes a danger that a driver must reckon with when it is still far down the road. In the worst case, the motorcycle is on a collision course even though it is out of sight, beyond an intervening bend or rise. The driver checks carefully, sees clear roadway, and begins his turn. But before he completes it, a motorcycle rounds the bend and collides with the car. Driver inattention has nothing to do with that kind of crash.

A speeding rider can also be in danger when the road is straight, level, and unobstructed because a driver has a limited decision horizon or span of road he checks before proceeding. He looks only as far as he must to make sure his maneuver won't interfere with traffic moving at the speed he expects to find on that road. It's an intuitive judgment, not a precisely measured one, but if a driver can safely cross 200 feet ahead of the normal 30-mph traffic, he won't worry about vehicles 300 feet away because he assumes they're moving at normal speed.

Even if a driver does see a motorcycle coming from farther away, he may not judge its speed correctly. When an object is moving straight toward an observer, the visual cue for speed is increasing size. Since a distant motorcycle is just a small point in the visual field to begin with, it doesn't grow noticeably in size until it is quite close. If it's far away, even an extremely fast-moving motorcycle is an inconsequential dot in the background.

A motorcycle's acceleration can be deceptive too. From a standing start, an aggressively accelerated motorcycle can cover ground in half the time it takes a car. A driver waiting to turn left might ignore vehicles stopped at a light a half-block ahead because they're too far away to be a threat. He expects a safe 10-second interval in which to turn, but he'll have only 5 seconds if one of them is a hard-charging motorcycle.

Finally, speed reduces a motorcycle's visibility to drivers because it decreases the time spent in a limited visual field, and that limits the chance of being seen. A driver preparing to turn may have to keep track of traffic coming in three different directions, so he's spending only one-third of his attention looking in any one direction. Traveling at 100 feet per second (70mph) a motorcyclist might not even be in the picture when a driver makes a quick glance toward him.

"Slow Down in Town"

When riding in an area where crossing traffic is a potential hazard, think about your speed and match it to the uncertainty of the environment:
  • Maintain speed consistent with the normal flow of traffic. When in doubt, obey the speed limit. It's often a good idea to be going slightly faster than adjacent traffic to stay out of blind spots. But if there is no adjacent traffic, that rule doesn't apply. And "slightly" doesn't mean 20mph.
  • Be able to stop in the distance you can see to be clear. When rounding a bend or cresting a hill, slow down so you can stop if you happen to find a vehicle crossing your path just out of sight.
  • Save the hard acceleration for open roads. Sometimes it's necessary to squirt ahead of a knot of vehicles to give yourself some breathing room, but accelerate only as hard as necessary to improve your position and don't exceed the prevailing flow of traffic.
In a Sport Rider magazine riding tip, Nick Ienatsch offered this excellent advice about speed, under the heading "Slow Down in Town":
Slowing down gives your brain a chance to notice things and more time to react. Your peripheral vision widens and you relax enough to read and predict traffic. Try walking down the supermarket aisle and reading labels, then try running down the same aisle. Now imagine all those soup cans are about to jump into your path and you'll see how slowing down affects your perception. There are plenty of places to go fast, but in and around traffic isn't one of them. If you can't slow down in town, put me in your will.

Excessive speed on the part of the motorcyclist contributes to one-quarter of Bay Area fatalities in crashes with crossing vehicles, and the tactics recommended here can help prevent them. Riders running red lights account for another quarter. It should be obvious how those can be prevented. But what about the other half, where drivers are at fault? They too, are preventable--most of the time, at least. Tactics for dealing with them will be the subject of another post.

Motion Camouflage
As it attacks prey, a dragonfly hides itself by flying in a straight line directly toward the victim, so it looks like a stationary object in the background. The same effect can make a motorcycle go unnoticed in traffic.
Quote:
Happy Hornet wrote: I shake my bike for some reason this always gets their attention

Quote:
4tuneit1 wrote: i usually always make a swerving motion back and forth slightly to get the drivers attention with my headlight. It helps the drivers determine my distance better i gather too.

Excellent advice. An article in the UK magazine Bike suggests why that works. Oddly enough, according to their safety expert, the answer is related to how insects attack prey.

When attacking, a dragonfly stays directly in the line of sight between its potential dinner and a fixed point in the distance. If dinner moves, the dragonfly alters its path just enough to stay on that line of sight. This tactic has the effect of keeping the predator at the same point in the prey's visual field. Because the victim sees no change in the big picture, it doesn't notice the motion and is unaware of the impending attack.

This effect is called motion camouflage, and it works because motion is difficult to perceive when it is directly along the line of sight. Since the object is stationary relative to the background, an observer doesn't see a change in the overall image and thus isn't cued to the presence of a moving object.

Though an approaching object increases in apparent size as it gets closer, it grows slowly when it is far away and will go unnoticed, especially if it is small. But as it gets closer, apparent size increases more rapidly. Moving from 1000 feet away to 900 feet, little change is seen. Advancing from 200 feet to 100 feet takes the same amount of time as 100 feet of movement at the greater distance, but the increase in apparent size is much more noticeable. Eventually the object seems to grow suddenly in size, and the motion camouflage is broken. That is called the looming effect.

A motorcycle is susceptible to motion camouflage because it is just a one-dimensional point in a driver's visual field when it is far away. And, according to the Bike article, when a driver is startled by the looming effect as he suddenly becomes aware of the motorcycle, he may freeze in his tracks. That would account for stories about the oncoming left-turner who stops in the middle of an intersection, making a bad situation even worse.

Duncan MacKillop, the riding instructor who related motion camouflage to motorcycling, suggests that diverging from a direct line of sight will break the camouflage and get the driver's attention:

I observed a smooth, gentle, single, zigzag motion, at any point along the line, created a rapid edge movement against the background and destroyed the motion camouflage. Drivers' eyes snapped towards me and they froze the movement I swept left to right and back again.

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Old June 17th, 2010   #2
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Default Re: Motion Camouflage and the Looming Effect

Good stuff, Rando.

I've used the "waggle" move effectively many times. Even just changing lane position in your lane will make you more visible.

If you have headlight modulators, turning them while in high traffic situations helps too. When I had mine, I would use them for intersections and in-city or in-town riding but, I generally turned them off on the freeways as I found it tended to annoy drivers. That is, unless I wanted to get a driver to move out of the passing lane so I could get by. (grin)
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Old June 24th, 2010   #3
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Default Re: Motion Camouflage and the Looming Effect

Excellent information! Motion camo is a new concept to me and makes perfect sense.

Also important in the left-turn-across-my-lane scenario is to place yourself where you are most visible to the turnee. If you are following a car, you may be screened from view - especially if you are following too closely. If you move to the left in your lane, you will be more easily seen. This seems counter-intuitive at first since you usually want to move away from a hazard, but being seen is the key. Not a guarantee, but an advantage.

Also, approaching the intersection, do not flash your highbeams. That may be interpreted as an invitation to go ahead. I wonder about the use of headlight modulators for this reason.

Be visible. Be seen. Be ready.

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Old June 25th, 2010   #4
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Thumbs up Re: Motion Camouflage and the Looming Effect

Tanks Randoman . . . good stuff to know .

This article help understand why and how bad thing . . . sometime happen to us ,rider.

Daniel

Last edited by LEINADEUGAL; June 26th, 2010 at 05:45 AM.
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Old June 25th, 2010   #5
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Default Re: Motion Camouflage and the Looming Effect

Another aspect of this is the effect of headlights. We generally consider headlights to be a visibility aid, but in daylight they can make the motion camouflage effect worse, because all they can see is a single (well, double in some cases) point of light, rather than the whole motorcycle. As a result, they are more likely to see you, but they are also more likely to misjudge your speed! (At least, that is one theory.)

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Old August 27th, 2010   #6
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Default Re: Motion Camouflage and the Looming Effect

Very good information, thanks for posting
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Old September 4th, 2010   #7
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Default Re: Motion Camouflage and the Looming Effect

Quote:
Originally Posted by na1g View Post

Also, approaching the intersection, do not flash your highbeams. That may be interpreted as an invitation to go ahead. I wonder about the use of headlight modulators for this reason.
Agree with the advice not to flash your high beams. But I've ridden with and without headlight modulators since about 1980, and modulators dramatically reduce the frequency with which people pull out, or start to pull out, in front of me.

Modulators cycle the light much faster than you could flash the brights yourself, so the visual impact is, I think, much different.

I don't, however, think it's a good idea to leave your modulator off and turn it on only when approaching an intersection. That could lead to confusion over your intentions.
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