2.2: HOW VISION AFFECTS YOUR ABILITY TO DRIVE

Your sense of sight is the most important of the senses that affect your ability to drive. Over 90 percent of the decisions you make while driving are based on information you gather with your eyes. 

Why is Good Vision Critical to Driving Ability?

Being able to see well means more than having 20/20 vision. It means being able to see straight ahead, to the sides and being able to perceive depth as well as color. You will have difficulty adjusting your car’s speed and position to minimize risk if your ability to see clearly is impaired. You will have trouble identifying signs, signals, roadway markings, and will not be able to scan the roadway far enough ahead to spot threatening conditions.

Visual acuity test measures how well you can see and whether or not you need corrective lenses to improve your vision. 

Field of Vision

Your field of vision is being able to see what is directly ahead and at an angle to your right and left when looking straight ahead. 

Your area of central vision is a narrow beam directly in front of you where your peripheral vision is at angles to your right and left that enables you to notice objects and movement to your sides. 

How Can You Compensate for Vision Problems

Practice judging the distance between two objects for poor depth perception, learn the meaning of signs and signals by shape and position for color blindness and drive slower than you would in the daytime for night blindness.

Poor Depth Perception

Depth perception helps you judge the relative distance between two objects, estimating the distance between yourself and the object. Depth perception and distance judgment work together when you drive because they help you control your following distance and adjust your position in traffic. To compensate for poor depth perception, increase your following distance.

Color Blindness

The most commonly used colors in traffic are red, green, and yellow. If you have normal color vision you won’t have a problem recognizing these colors when you see them. Some people are color blind and unable to tell the difference in these colors. However, color blind individuals can drive safely by telling the meaning of signs and signals by their shape, position and by reading the words printed on them. 

Night Blindness

Even if you have 20/20 vision at night your visual acuity, field of vision, depth perception, and color vision are all reduced. One of the biggest problems in night driving is glare caused by the sudden brightness of the headlights of oncoming vehicles. 

Don’t look directly at the headlights of the oncoming car, instead look directly to the right edge of the roadway keeping the approaching vehicle in your peripheral vision and reduce your speed.