Fog / Snow Lights?

[unwiredadventures]

I drive up in the San Bernardino several times per month.

Several times each winter I find myself in complete whiteout and extreme fog conditions.

Which is the best light, color, etc. to use in these conditions?

[cruiserlarry]

I drive up in the San Bernardino several times per month.

Several times each winter I find myself in complete whiteout and extreme fog conditions.

Which is the best light, color, etc. to use in these conditions?

This is a topic I could discuss for hours, and a complete discussion isn't possible in a post. But here is some basic information that might help:

Fog lights, regardless of the light color, are designed to illuminate the area under the fog (which usually sits a couple of feet off the ground), and does not penetrate the fog as some think. No automotive light will shine through water vapor. The idea is to light the ground under the fog to help make the road more visible to the driver. A fog light distinguishes itself with its light pattern, which is wide and flat, with a sharp upper cut-off to prevent reflection back at the driver. Fog lights, because of their unique pattern, are also used as cornering lights, as the wide pattern helps the driver to anticipate curves on mountain / winding roads, and to better see the road boundaries.

Fog lights are available in both yellow and white - and while the benefits of either can be argued ad nauseum, it generally boils down to personal preference. Some feel the yellow light helps reduce the reflected glare, making the light easier on the driver's eyes, and the light pattern easier to discriminate.
Others find the yellow coloring distracting, and prefer the purer white color to prevent eye fatigue. I feel you should try both, if possible - maybe drive in someone's vehicle that has one or the other, and decide which works best for you. I have used both over long periods of time, and find both work well - with little fog in SoCal, I prefer white for it's use as a slow speed trail light and cornering light.

Another critical issue (and more important, IMO, than light color) is the location of the light itself. Because of their wide, flat pattern, fog lights are more functional when place as low as possible on a vehicle. They should be positioned as far apart as they can be, and be sitting low enough to be focused forward with a slight downward beam - this will provide the largest area of usable illumination, especially in low lying fog banks.

One final note: Fog lights are useless in Tule Fog, which is a phenomenon where the fog clouds literally touch the ground. As fog is water vapor, and light does not penetrate water vapor effectively, even fog lights won't help where there is no open space under the fog cloud. So, while fog lights can dramatically assist the driver in foul weather conditions, cornering / windy roads, and on slow trail driving, no light will do much for you if you get stuck in a Tule Fog situation - time to get out and walk !!!

Hope this helps you out...

[unwiredadventures]

This is a topic I could discuss for hours, and a complete discussion isn't possible in a post. But here is some basic information that might help:

Hope this helps you out...

This helps. I need to find something that I can mount low.

Thanks!

[gon2srf]

Awesome description Larry. I really had no idea that fog lights were designed to work under the fog. I have found that in really bad "Tule fog" I can see best in the FJ with just the DVL's only.

[cruiserlarry]

Awesome description Larry. I really had no idea that fog lights were designed to work under the fog. I have found that in really bad "Tule fog" I can see best in the FJ with just the DVL's only.

Thank you - I am a bit of a lighting nerd

Your experience is a good example of my point regarding light and water vapor. When faced with Tule fog, it's like shining into a mirror. Any bright light will just shine right into the driver's eyes. Minimal lighting, enough to let you recognize objects and movement, are best if you must continue to drive.

[BlueFJ]

Scott, what are DVL's?

[unwiredadventures]

Scott, what are DVL's?

I think they are DriVing Lights.

[BlueFJ]

Scott, what are DVL's?

I think they are DriVing Lights.

Ok, that would make sense as it's my experience that driving with low beams is always best in fog and high beams just make it worse.

[gon2srf]

The DVL's are even lower power than the lowbeams. They work great in the thick stuff.

[cruiserlarry]

I think he's referring to DRLs - daytime running lights - which, on the FJC, power the high beams at about half voltage. This won't give much illumination, but doesn't produce much glare, either.

Driving lights (my next lecture ) are narrow-beam, high power lights designed for higher speed straight line driving. They are worse than high beams in a fog situation....