In the Treasure Valley, fog is a weather phenomenon that usually only occurs in the colder months of the year. According to the National Weather Service, it is most common in the days between Thanksgiving and Valentine’s Day. Though the fog in Treasure Valley is usually advection fog (fog that moves in from another place), it can become rather dense and significantly reduce visibility.
In a perfect world, you would be able to avoid driving in foggy conditions and wait for better visibility. But, realistically, that just isn’t always possible. Luckily, fog lights were created to help make your journey safer.
How Do Fog Lights Work?
Fog is made up of tiny water drops or ice crystals that float in the air near the surface of the ground, which can look like a low cloud. Not only can the dense quality of this air make it difficult to see, the water drops, and ice crystals make things even worse because they reflect light. For this reason, driving through fog with headlights can become rather dangerous. You should never use high beams in the fog. Fog, though low lying, does not touch the ground. It usually hovers between 12 and 18 inches over the surface. Because of this, factory-equipped fog lights are installed low on the vehicle. The lights are designed to have a sharp cutoff angle at the top so that no light shines up to reflect off the fog and strictly lights the road ahead. While fog lights do not have the same reach as headlights, they do light up enough of the road to allow you to slowly reach your destination. And because they don’t just reflect light back to you, you are more visible to other motorists too.How are Fog Lights and Headlights Different?
Headlights are designed to increase your visibility at night and to allow you to be seen by other drivers. However, they were designed for clear conditions. Fog lights and headlights are different in both their construction and placement. Fog lights are made to shine light low and only onto the street. Headlights are placed higher to show you what is ahead further on the road and to the side of the road. They also make it so that other motorists are aware of your position on the road when it is dark outside. You will also find that fog lights are often yellow, whereas headlights are usually white. Fog lights are commonly yellow because yellow light has a stronger wavelength than white or blue. It is believed that the stronger wavelength can penetrate through the dense air of fog increasing visibility. However, the light location and angle are much more important.Using Fog Lights in Idaho
As with using high beams, there are rules on how to use fog lights properly. Some of these rules vary from state to state. Idaho State Legislation has listed the following rules for fog light use:- Fog lights and low beam lights may be used together.
- Two front-mounted fog lights are allowed.
- Headlights should only be used in the daytime if visibility is under 500 feet.
- Fog lights cannot cause a glare in the eyes of oncoming drivers.
