Tactics: Nightsight

Riding Technology

By Bill Hampton

For night riding, the two-point...

read full caption

Sport riding at night has a certain enchantment of its own. With your bike's Cyclopean headlight probing the inky road ahead, you feel as though you and your bike are floating in some dimensionless realm through the opaqueness of the night.

Yes, motorcycling at night can be enchanting. But it can also be dangerous-very dangerous. And the reason is obvious: You simply can't see as well as you can during daylight hours. Regardless of how good your daytime vision is, your nightsight suffers by comparison.

<+?E? not hopeless; you can learn to work with your eyes' natural functions to see more effectively at night. First, consider how your eyes work under conditions of low light and darkness. In daytime you see something clearly by looking directly at it. The reason is that light sensors called cones are located in the center of the eye. However, these cones are ineffective in darkness. Other sensors called rods come into play; located on the fringe areas of the retina, the rods are sensitive to darkness.

But to take full advantage of the rods, you need to look at something with your head turned slightly to the side. Most of the time, both rods and cones work together, unless you're exposed to total darkness.

As during daylight, you'll see more when you take an interest in your darkened environs. Of course, it's more difficult to sustain attention on your riding environs when they're immersed in darkness or low light. Sometimes a solitary source of light can hook your attention and cause you to become disoriented.

For instance, let's say you've been riding all day and into the night, and you're tired-dog tired. You're on your way home out in the boonies somewhere when a distant farmhouse light catches your attention. It becomes a hypnotic stimulus. Each time you look at it, you fixate on it a little longer, and you don't see the curve sneaking up. Well, hopefully you do.

This phenomenon is called stare vision. Sometimes the light may even appear to be swinging in an arc. The sneaky thing about visually locking onto a light stimulus is that you aren't aware of doing so. When boredom and fatigue cause your brain to shut down for lack of stimuli, you can become mesmerized by anything that looks remotely interesting.

When you interfere with your eyes' capacity to scan freely, you set yourself up for a kind of self-hypnosis. You need to scan your darkened surroundings to keep your brain's visual/cognitive centers open.

Along with scanning, see that you're blinking normally. Blinking does a couple of things: It provides the eyes with a momentary rest, and it enhances circulation within the eyes. Every so often you might want to squeeze your eyelids shut for a moment to intensify the aforementioned benefits.

Scanning and blinking can also help you cope with the potentially dangerous effects of oncoming headlights. That car approaching you with its headlights shining up at the trees can dazzle you to the point where you get disoriented and lose your position on the road.

You can close your left eye and focus the right one on the right side of the road, but you'll lose peripheral vision on the left. Should the other vehicle drift onto your side of the road, you might not notice in time. You can also keep both eyes open and focus on the right side of the road. But again, you'll lose peripheral vision by keeping both eyes focused in only one direction.

Try the two-point scan instead. It consists of shifting your line of sight (both eyes open) between two constantly changing points on the road: one directly in front of your bike and the other opposite the oncoming vehicle on your side of the road (see illustration). Keep your eyes moving in this fashion until the offending vehicle passes by.

The two-point scan serves two purposes: It allows you to avoid the direct glare of the oncoming headlights, and you still have enough peripheral vision to monitor the position of the other vehicle in case it drifts into your lane. Along with scanning, blink normally to help minimize eye fatigue. Blinking keeps the eyes lubricated, which further reduces headlight glare.

You may think that shaded eyewear is effective for combating headlight glare, but it severely reduces vision toward the darkened side areas (and an untinted face shield is a must). Sunglasses can be worn inside in brightly lit places; they help your eyes adjust readily to darkness later when riding.

Difficulty in adjusting to darkness or low light after having been exposed to bright light could signal a vitamin A deficiency. Ditto for being hypersensitive to headlight glare. Don't be deluded, though, into thinking that huge doses of vitamin A will correct these problems and give you cat's eyes at night. Too much of this vitamin can be toxic. Besides, there could be some other problem with your vision. That's why eye exams are so important. If you have a nightsight problem, find out why.

For example, if your depth perception suffers at night to the point where a vehicle you're following has hazy, smallish taillights, you could have a visual weakness called protanopia. It's a condition whereby the retina is not responsive enough to the color red. So another vehicle's taillights will indeed appear small and hazy. If your depth perception is off enough at night that you're having too many rear-ending close calls, get your eyes checked.

The hazards you face at night are the same ones you deal with in daylight. It's just that you can't see them as well.

This story was originally published in the June 1995 issue of Sport Rider.