Vanishing Act
A key factor in being seen is traveling at a speed that other motorists expect.
One theme in this thread is that driver and rider education don't teach us to think about speed in ways that promote safer riding. All we're ever taught is that the speed limit is probably safe, and that anything over it is dangerous--a distinction we quickly learn is meaningless. This deficiency is glaringly obvious when discussion turns to speed enforcement. An opinion often expressed by those who like to ride fast is that speed limits are created for one reason: to separate them from their money. But while enforcement practice is sometimes about emptying your pocket and filling the government's, the limits themselves usually exist for a good reason: They make traffic predictable so drivers can maneuver safely on the roadway. When speeds match the surroundings, motorists can make turns, enter and exit parking, yield to pedestrians, and accommodate other activity with little risk of a crash.
A rider who doesn't understand why the limit is what it is and ignores it arbitrarily can endanger both himself and others. Because the posted limit represents underlying constraints of the road and surroundings, he must grasp those constraints before deciding he can ignore the limit. Maybe at 3:00am Main Street is deserted--no traffic, no pedestrians, no parked vehicles--so a 60mph wheelie in the 25mph zone doesn't create much danger. But at noon, with all those hazards present, it could be deadly. Recognizing elements that constrain speed is essential for distinguishing between good speed and bad speed.
These environmental constraints create expectations among motorists about speed--reflected in the limit--and they adopt driving habits that make it possible to accommodate traffic at expected speeds. But they see what they expect to see--the unexpected, not so much--so excessive speed can practically make a motorcycle disappear.
Out-riding your sight distance
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 rise or bend. The driver checks carefully, sees clear roadway, and pulls out. But as he does, a motorcycle crests the hill and collides with the car. Driver inattention has nothing to do with that kind of crash.
Extraordinary speed in ordinary traffic
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 crossing traffic. He looks only as far as he must to make sure his maneuver won't interfere with vehicles 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 150 feet ahead of the normal 30-mph traffic, he won't worry about a vehicle 200 feet away because he assumes it's moving at normal speed. However, if it's a motorcycle doing 60 mph, it's just 2 seconds away and in immediate danger from the car pulling out in front of it.
The difficulty of judging speed
Even if a driver does see a motorcycle coming from beyond his decision horizon, he may not be able to judge its speed very well. When a motorcycle is moving straight toward an observer, it is a stationary dot in his field of vision. The visual cue for speed is increasing size, but since a motorcycle is just a small point in his visual field to begin with, it doesn't grow noticeably until it is quite close. Thus, the observer can't perceive its speed accurately and sees a fast but distant motorcycle as merely a dot in the background.
The acceleration deception
A motorcycle's acceleration can be deceptive too, because from a standing start, an aggressively accelerated bike can cover ground in half the time it takes a car. A driver waiting to turn left might be watching for traffic in several directions, so no potentially interfering vehicle gets full attention. He sees vehicles stopped at a light a half-block distant but ignores them because they're too far away to be a threat, and he turns his attention elsewhere. But while he may expect a safe 10-second interval from traffic at that light, he'll have only 5 seconds if one of them is a hard-charging motorcycle.
Limited opportunity to be seen in the mirror
Finally, speed reduces the visibility of a motorcycle to vehicles ahead traveling in the same direction because it decreases time spent in the mirror field, and that reduces the chance of being seen by a motorist scanning for traffic approaching from behind. The driver may check his mirrors carefully enough to spot a vehicle traveling 5 or 10 mph faster than he, but not enough to see a motorcycle going substantially faster. If the motorcycle overtakes at +20mph, it will be in the visual field covered by the driver's mirrors only one-fourth as long as it would if it were at +5mph. One-fourth the time means one-fourth the likelihood of being seen.
We all enjoy the acceleration and speed our machines are capable of, but when excessive speed creates a situation where our safety depends on other motorists anticipating and accommodating it, we're in trouble. Because most likely they won't.
Rules offered earlier in this thread will make it easier for others to see you:
- Maintain speed that allows you to see the roadway at least 4 seconds ahead.
With a clear view 4 seconds ahead, you're not going to be surprised by hazards revealed as terrain opens up or as you clear obstacles--and other drivers won't be surprised by you. If a threat appears, you'll be able to stop without resorting to emergency braking, which also protects you from vehicles behind that could rear-end you. More details in this post.
- Go with the flow.
Recognize the tempo of traffic and ride in synchrony with it. By matching speed and acceleration to the prevailing flow, you become part of it at a speed other motorists are expecting.
- Match the mode to the road.
Make a sharp distinction between opportunities to enjoy sport riding, and situations that offer little reward for high risk and demand your best to negotiate safely even at moderate speed.
