Night Blindness

While driving down a dark, twisting two-lane road, the glare of an oncoming vehicle’s high beam headlight suddenly appear.  The vehicle flashes past and for the next two seconds you are blind.  You have just experienced a common hazard known as night blindness. 

Night blindness occurs when the eye is accustomed to low levels of light and the light intensity suddenly rises.  The eyes attempt to adjust to the new light level, but if that level of intensity is only momentary, then the eyes have to re-adjust to the lower level.  With the eyes trying to make these adjustments, there are several seconds that the vision is impaired.  During the day, we are able to gather about 85 percent of the visual information needed to drive, but at night all of this changes.  At night, it becomes difficult to detect objects from the surrounding darkness because we lose much of our contrast sensitivity (the ability to distinguish objects and hazards from the background).  In addition, our peripheral vision is sharply reduced and virtually gone on unlit roads.  Under the best conditions, headlights limit our visual range to the areas that are illuminated, which is only 250 to 350 feet of the road ahead. 

If a driver turns his or her head from side to side, instead of taking a quick glance, it will help make up for the lost side vision that occurs at night.  If the driver must wear glasses to drive, frames that have thin sidepieces should be selected, since large or wide sidepieces hinder side vision.  Also, slower driving speeds will allow more time to detect a hazard and respond in a crisis. 

Because night driving is often necessary for professional drives, special precautions must be taken to avoid collisions that may occur as a result of night blindness.  The following are some “Do’s “ and “Don’ts” to practice for driving at night:

Do: 

• Drive within the range of your headlights, not by what you think you can see beyond your headlights. Slow down so you can stop within the range of your headlights.
• Adjust your mirrors to the “night” setting to avoid headlight glare.
• Avoid being blinded by oncoming headlights by focusing your eyes toward the right side of the road.
• Keep your headlights clean.  Dirty headlights do not project as far in front or side to side.
• Clean your windshield and all other windows inside & out to reduct headlight glare and visual distorting object outside the vehicle.  Window film, especially inside the vehicle can take a single headlight beam and have it spread over the entire windshield causing a blanket of glare.
• Keep your eyes moving between the road and your mirrors
• Turn your head from side to side to increase your peripheral vision.
• Use your high beams when you can.
• Take off sunglasses at dusk.
• Whenever possible, drive on interstate highways which provide better lighting and more distance between oncoming headlights, instead of darker country roads.
• Turn your instrumental panel lights down to reduce the glare on the inside windshield and side windows.
• Remember, as you grow older,  your night vision can deteriorate.

Don’t

• Don’t exceed the speed for driving conditions especially on unlit or winding roads.
• Don’t use tinted glass or tinted strips on windows & windshield.
• Don’t depend on fog or parking lights when driving at dusk or dawn.
• Don’t keep high beams on when another vehicle approaches.
• Don’t keep your interior lights on while driving your vehicle.
• Don’t stare into your side view mirrors as cars pass.
• Don’t use any type of medication that may change your night vision or cause drowsiness.

Humans are not designed to have the eyesight of creatures of the night, so remember to respect the road, the darkness and your ability to see.