Glare — a sensation caused by bright light in one’s field of view — is a serious problem for drivers. It can reduce a person’s ability to see clearly, and at times, even cause temporary blindness. What’s more, glare can create feelings of annoyance, discomfort or even pain, which can distract drivers further, causing them to slow down, drift in their lanes or miss objects in and alongside the roadway.
Glare has gotten worse. More and more cars and trucks are being equipped with fog lamps or other auxiliary lights in front. There is more widespread use of halogens and high-intensity discharge lamps with their bright blue-white light.
Glare decreases seeing distance because it causes light scatter within the eye, causing a haze of veiling luminance that decreases contrast and reduces visibility. This diminishes the ability to perceive the visual information needed for a particular activity. The effect is known as “disability glare.”
The greater the intensity of the glare light, and the closer the glare light is to where one is looking, the greater the disability glare will be.
Research by the National Highway Traffic Safety Administration (NHTSA) found that disability glare can lead to the following effects:
- Decreased “visibility distance” — the distance at which an object can be seen.
- Lengthened reaction times. As the intensity of the glare increases, drivers’ reaction times to objects in and along the roadway become longer.
- Increased recovery time. After the glare passes, the glare has a lasting effect that increases the time it takes for a driver’s eyes to recover. During that time, the visibility distance is reduced and reaction times are increased.
According to the AAA Foundation for Traffic Safety, it typically takes a driver 10 seconds to recover from headlight glare. At 60 miles an hour, a vehicle can travel about a quarter mile in 10 seconds while the driver has reduced vision, increasing the risk of an accident.
After dark, the most common type of glare is that of oncoming headlights or the reflection of headlights in rearview mirrors from following vehicles.
Two-lane highways, as compared to multi-lane roadways and expressways, may present the “worst-case” scenario for nighttime glare, NHTSA research found. Among the reasons for this were:
- Two-lane highways are typically unlighted, so in addition to reduced visibility, the brightness difference between headlamps and the roadway is higher.
- Because of the closer proximity of oncoming glare, the headlight beam pattern is directing more light at oncoming drivers.
- Two-lane highways often have complicated roadway geometries, such as sharper curves and steeper grades, which exposes drivers to a higher range of oncoming headlamp glare.
When experiencing direct and blinding forward glare, traffic safety professionals say drivers can reduce the glare’s effect by looking toward the right side of the road and watching the right edge of the road, using it as a steering guide.
For glare in mirrors, drivers can do several things, these professionals say: quickly adjust or correct their mirrors so the glare is directed away from them, turn their eyes away or shift their seating position.
Drivers can also be blinded by bright sun low in the sky and sunlight as it hits the windshield or reflects off other vehicles or objects.
Traffic safety professionals emphasize the importance of keeping windshields and windows clean — inside and out. A dirty windshield worsens the problem because dirt, streaks and smudges are magnified by glare and scatter light rays.
When cleaning the windshield and windows, they say it is also a good idea to clean the wiper blades using a paper towel dipped in windshield washer fluid. This removes grime and oxidized rubber from the edge of the blade and helps prevent streaking. If streaks persist, the blades need to be replaced.
Traffic safety professionals advise repairing any minor windshield abrasions, rock chips or cracks immediately. Further, the professionals recommend turning on headlights so as to be better seen by oncoming traffic in glare situations. Drivers are also advised to drive cautiously and to leave enough following distance to ensure ample reaction time to a situation ahead. BI