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Thinking About Darkness and DrivingDriving at night is no longer a simple matter for me. As a matter of fact, for most older drivers, darkness presents a real problem because our eyes do not let in as much light as they did when we were younger. Previously I mentioned research which shows that as we age, there is an actual decrease in the size of the pupil, that part of the eye which allows light to enter. At age 60, we need three times as much light to see well as we did at age 20! How do I compensate?I do tend to drive more slowly at night. Why is reduced speed important for night driving? When we drive we are actually using two different visual functions: peripheral and focal vision. Peripheral vision helps me keep the car in its lane. Since my car lights illuminate the side of the road, I would expect to have no problem driving at normal daylight speed. However, my focal vision is limited to the road area which is illuminated. You may have heard the warning, "Don't overdrive your headlights." This warning cautions us that since we cannot see objects beyond the lighted roadway, we must limit our speed for safety. Night driving is not the only time when darkness might cause a problem. Now that I am older, it takes me longer to adjust from light to dark and back again. Traveling through tunnels makes me quite aware of this problem, though I have even noted it when the clouds temporarily obscure the sun and then part again. Harvard research showed that the time it takes to recover sight after an adjustment from light to dark or dark to light is directly proportional to the driverŐs age. And, at night, the glare from oncoming traffic can create a similar problem. When another carŐs lights are shining in your rear-view mirror or coming at you from the opposite direction, it can feel just like driving in bright sunlight. When the headlights are past, you must adjust to the sudden darkness until other headlights force your eyes into yet another adjustment. And so on. I do not completely restrict my nighttime driving. Here are some of the questions I ask myself before getting behind the wheel after dark: How tired am I? Am I feeling uneasy about driving in the dark? Am I driving to a familiar place on familiar roads? Is anyone coming with me who might assist me in navigating or seeing direction signs or road hazards? If the answer to any of the questions indicates a risk to safety, I do not drive. But when I do feel comfortable, I remember to reduce my speed and to drive on familiar roads. I find it helpful, too, to ask myself whether that trip I think I must take is really necessary. If it can wait until daylight, so much the better. Some years ago, I attended a large meeting on auto safety. Dr. Ward Edwards, a Statistician and Professor of Economics was the moderator. He started the meeting with a betting game to demonstrate the risk of driving. First he asked how many of us would place their name and a dollar in his hat. He would draw a name and the winner would take the pot. Nearly everyone raised a hand. Then he said, "who will play another game with the same odds? I will draw one name out of the hat and he will pay everyone a dollar." No one volunteered.
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