Purpose of Fog Lights

by Heather Broeker

We see them from our cars as we drive down rural roads on dark foggy nights. We were also probably tested on them a long time ago during driver education classes. They're fog lights---man-made illumination located on your car's light switch. But when do you use them, and what exactly is their purpose?


Most cars, at least new ones, are equipped with fog lights. They are low beams that help you see through the fog. If you were to use your regular or high-beam lights, the light projected straight into the fog would bounce off the fog and reflect in all directions. This would, of course, make it harder to see the road and other traffic.


Fog lights, which only light the ground immediately in front of your car, are mainly for very foggy conditions when you are traveling slowly due to limited visibility. They can also sometimes be used on dark windy roads in the middle of the night. On a sunny day, you will likely not even notice your fog lights, and there is really no purpose in using them during these times.


Some fog lights are yellow, while others are white. There is a debate as to which ones work better. Some people believe that since yellow light has a longer wavelength than white light, it is not as likely to be reflected. The fact is, research shows that there is really no difference.

Fog Behavior

Fog generally hovers at about 10 to 20 inches from the ground. So, in theory, if we project light out into the pocket that does not contain the fog, you can brighten the road for a distance that will allow you to see farther. Low-mounted lights---or fog lights---are installed at your bumper or even lower, and the light they expel is actually cut off at the top, creating a light pattern that projects straight out, then flat and then down, but not higher.

Worth a purchase?

Some people swear by fog lights; others say they're pointless. If you live in a high-fog area, they may be worth a try. Just make sure you buy a high-quality fog light and have it professionally mounted, because the position of the light will greatly affect its performance.

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