Originally Posted by def
First of all, there is no science that I have found that yellow lights (longer wavelength than white) improve your vision or conspicuity in fog.
Most so called fog lights are mounted very low on the auto or truck because fog usually sits a couple of feet off the ground and so, low mounts can improve driver vision somewhat.
But yellow light is not the most efficient light for the human eye to perceive. The sweet spot for the human eye is about 4500K, the temperature for OE HID automotive headlights.
Riding or driving in fog is very dangerous because most of the light from your headlights is reflected back into your eyes from the water vapor. Also, the water vapor (fog) allows poor travel of light from oncoming headlights and so, you don't see the oncoming vehicle until it is very close. Following vehicles is even worse because most rear lighting on vehicles is limited to only a few watts. If you are travelling in fog, you're better off having a bright light pointed to the rear so people don't rear end you.
Retroreflective material on a jacket or helmet helps also.
I ride in fog all the time, letting that stop you harkens back to people who advertise their rides as "never ridden in the rain", just doesn't make much sense...
One of the best rides I ever had was an early morning ride in south east South Dakota (coming off the dam who's name excapes me), I was listening to some Wagner and as my elevation changed, I came in and out of the fog bank into one of the most glorious sunrises ever, that is one ride of many rides that I will never forget...
As far as the color and wavelength of light you are correct, it isn't really going to help, having said that, I do like my addional amber LED's I have on mine, having the different wavelength (and properly aimed, I have a dissertation on here somewhere about that) gives a more complete color rendering and DOES help things like road signs "pop".
Yes, riding in fog presents challenges, just like riding in rain or snow, if you take the proper precautions, none of them should stop you from enjoying your ride.