My big fog experience was on Skyline Drive, in the Shenandoah Mountains of Virginia. I was returning to New Jersey from a trip to Great Smokie Mountains, and I ran into a heavy fog condition. Visibility varied between 10 and 20 yards/meters.
This is a windy mountain road, two way travel (one lane each way) with no dividers. Normal speed limit is 45 mph. In that fog, you rally had to take it slow, maybe 10-15 mph. My biggest concerns were someone coming the ohter way and being over the line or getting hit from behind because it would be very hard to see the small R65 taillight until you were on top of it. I figured more lights are better, and not having flashers, I put on a turn signal. After about five minutes or white-knuckle riding in the fog, I came up on a group of about 10 motorcyclist. The pack of taillights was a lot move visible than my single one with a turn signal, so I just latched on to the end of their group and rode with them for about a half hour. The pack mentaility seemd to work well. A few cars came up on us, but never dangerously close.
I planned to peel off into a rest area and get dinner there, but they pulled in there too. As I was walking in, they invited me to sit with them. I accepted. I started talking with them, and found out they were from New Jersey too. They asked where I was staying that night, and I told them I was planning to get a site the national park campground. They said it was all full, but I could just ride in with them and throw a tent in their area. I did, and hung out with them. Turned out they had a support van with them, and three giant coolers of beer, mixers, and liquor, so we partied late into the night in the rain. The park rangers were none to happy, and were going to kick us out at 2:30 in the morning -- but that is another story.
So the fog story ended well for me, but I would not like to ride in a fog like that again.
k_enn