My
2005 post from the
Motorcycle Consumer News forum:
Motion camouflage
An article in the March 2005 issue of the UK magazine Bike added a bit to the understanding of why cars pull out in front of motorcycles. Research on how certain insects attact prey was applied to the SMIDSY crash (sorry mate, I didn’t see you).
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. It doesn’t swoop out to “lead” its victim. This tactic has the effect of keeping the dragonfly at the same point in the prey’s visual field. Because the prey sees no change in the big picture, it is unaware of the impending attack. This is called motion camouflage.
Motion is difficult to perceive when it is directly along the line of sight. Because 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 the object increases in apparent size as it nears, the change goes unnoticed at first–moving from 1000ft distant to 900ft may not affect the image enough trigger a response. A motorcycle is particularly susceptible to motion camouflage because its cross-section area as seen by an observer is much less than that of a larger vehicle.
But as the object gets closer, apparent size increases more rapidly. At constant speed, an approaching object takes the same time to move from 200ft to 100ft as it did from 1000ft to 900ft, but the apparent size increase is greater. Eventually the object seems to grow suddenly in size, and the motion camouflage is broken. This is called the looming effect. According to the Bike article, when an observer is startled by the looming effect, he may freeze in his tracks. If the observer is an oncoming left-turner, he may stop in the middle of the intersection, making a bad situation even worse.
Duncan MacKillop, the riding instructor who related motion camouflage to motorcycling, suggests that diverging from the direct line of sight will break the motion camouflage and get the observer’s attention. For example, a driver stopped at a cross-street on your right will be looking left at a slight angle to the path of the road. If you stay to the left of your lane, you will diverge from his line of sight, making yourself more noticeable. But if you’re veering right (say, moving from the left to the right lane) you’ll be moving along the crossing driver’s line of sight, helping to hide your motion against the background.
MacKillop recommends: “I observed a smooth, gentle, single, zig-zag 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.”
