Dusk-to-dawn driving can be downright dangerous
PRECISION DRIVING
By Bill Love
Auto Columnist
While driving between sunset and sunrise, we encounter our greatest odds of having accidents. According to the National Highway Traffic Safety Administration, nearly one-half of all accidents take place at night, even though those hours only represent 25 percent of total traffic. More sobering, the NHTSA reports that the nighttime fatality rate is three times higher than the daytime rate.
People often tell me that they are less confident during night drives. Part of that is due to my aging circle of friends, but beyond age, there are numerous factors that lend foundation to that less-than-confident feeling.
Darkness-induced vision shortcomings, lack of contrast in roadway objects, temporary blindness from oncoming headlights, excessive confidence, and overdriving headlights are all factors that can hamper the safety of drivers who are out at night.
We all have varying vision, but whatever our prowess of perception may be, it is diminished in the dark. For all drivers, depth perception, color recognition, and peripheral vision are all compromised after sunset. And age is indeed a factor. More light is required to see the same things as we age. The National Safety Council claims, on average, a 50-year old driver may need twice as much light to see as well as a 30-year old. In addition, the ability to adapt to sudden changes in light, and to refocus back and forth from short to long distances becomes more difficult with advancing age.
Besides age, though, there are many other vision-related woes that affect seeing with proficiency at night. Among them are medical conditions of the eye, such as astigmatism. That, along with impaired color vision, peripheral vision, depth perception, distance vision, or close-up focusing can occur at any age, and exacerbate the difficult task of night driving.
Research findings from the Pennsylvania Department of Motor Vehicles show that over half of those who fail a DMV vision exam are unaware of their vision problems. If you have doubts about your night vision, it is advisable to check with your eye doctor.
Even in the absence of a perceived difficulty, the American Optometric Society recommends that everyone under the age of 40 have a thorough eye exam at least every three years; drivers 41-60 every two years; and drivers over 60 every year.
When the eyes’ pupils are dilated in low light, drivers’ abilities to focus on potentially hazardous objects are inhibited. Coupled with the difficulty of seeing low-contrast objects (like a darkly-dressed pedestrian, or a moose) against a background of darkness, this makes night driving a challenge.
To enhance seeing successfully at night, avoid direct exposure to oncoming headlight glare – look toward the right side of the road, using its edge as a steering guide, as cars approach from ahead. Reduce your dashboard light illumination to enhance the ability of your eyes to adjust to darkness. Move your windshield-mounted mirror to the “night” position to reduce light “contamination” from vehicles behind. Clean your headlight lenses often in winter – dirty ones can reduce your vision ahead by as much as 50 percent. And for those who wear glasses, an anti-reflective lens coating is said to reduce glare.
Drive confidently, but not overly so. Drivers with excellent vision, and good equipment, still often overdrive their headlights. In other words, they drive at a speed requiring a stopping distance greater than the field of vision their headlights are lighting.
By the time an object is within the range of their vision, in those cases, it is too late too stop. That is why swerving is often a last resort, which can end in disaster.
Fortunately, the majority of vehicles on the roadways are now equipped with replaceable-bulb halogen headlights as opposed to the older sealed beam units. These lighting systems do a good job of showing the path ahead, but at higher speeds, the high beam setting is required to out-see your stopping distance. Most experts agree that on low beam settings, in otherwise total darkness, speeds over 35-40mph are excessive.
Required stopping distance at a given speed depends on the vehicle, along with the recognition and reaction time of the driver. With clean and properly aimed headlights, a driver can generally see 350-450 feet with high beams, and 200-250 feet with low beams.
Average times for drivers to recognize a hazard and react by applying the brakes vary from 1 to 2 seconds. Alert, professional drivers even exceed one-half second.
When an average reaction time is calculated into stopping distance for an average vehicle on dry pavement, the stopping distance from 60mph is over 350 feet. It’s easy to see that, even on high beam, you must be at the top of the illumination range to have a margin of safety. With low beams, you are simply leaving a “crash-zone” ahead of your field of vision at that speed. Average stopping distance including reaction time from 45 mph is about 200 feet.
Please drive according to conditions, and consider the limitations of your night vision.
Readers may write to Bill Love, c/o The Spokesman-Review Auto Section, P.O. Box 2160, Spokane, WA 99210. Or you may contact him via e-mail at precisiondriving@spokesman.com.
