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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883


Daylight wanes for drivers

As leaf colors change, available hours of daylight diminish.  This annual waning begins naturally about now and accelerates when we discard daylight savings time just after Halloween.  As winter wears on, hours of darkness predominate.

This yearly phenomenon is relative to driving because we encounter our greatest odds of having traffic accidents between sunset and sunrise. Since that period is much longer for the next few months compared to the last few, it’s time to up our readiness for it.

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% 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 there are numerous factors fueling 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.

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 to stop.

Whatever level of vision prowess we have, 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, 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.

When 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 a night driving challenging.

To enhance successful seeing at night, avoid direct exposure to oncoming headlight glare by looking toward the right side of the road, using its edge as a steering guide while cars approach from ahead.  Reduce you dashboard light illumination to assist the ability of your eyes to adjust to darkness.  Move you 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 you vision ahead by as much as 50%.  And for those who wear glasses, an anti-reflective lens coating is effective at reducing glare.

Please drive according to conditions, and consider the limitations of your night vision.

Readers may contact Bill Love via e-mail at