Oh I do so love it when someone asks a question about something that I've just read before I forget it.

...far more fog on the farm this year.
No one can rightly question this observation. Even though general statements concerning weather by casual observers are highly subjective and therefore suspect. You were there and we were not. - -
I agree totally with Bean and Bill and Hyla, but let me elaborate on some points that I won't remember next week...

You can't see light. That is until it is reflected off something. In a fog the reflection is provided by little particles of fog, so it would seem that visibility would degrade with distance. It does but in packets, with some colors absorbed first, green and blues first, reds and yellows later. low beam yellow fog lights help ,but in a deep fog the human eye-mind needs a frame of reference in which to judge depth and relative speed. The backdrop of swamp and median would serve to contrast and distinguish the parallel lines of the interstate. More so, a concrete surface would reflect light better than green stuff.
Well isn't that interesting, but it's probably has little to do with what you saw. - -

I've noticed that even when the fog is nearly impossible to drive through on country roads without being in danger of going off the road, when I hit the interstate, the fog is divided between median and the woods, marshes, farmlands to the right. It appears to be a phenomenon.

Radiation fog is the caused by the cooling of the ground at night. This allows evaporation at a lower dew point. The process of evaporation warms the air and radiates the warmth upwards. on clear star filled nights when there are no clouds to reflect the radiation back down to earth, fog is formed. This is probably not what you saw. - -


An Upslope fog is formed when moving air is forced to rise upward over mountains where the atmospheric pressure is less, the air is cooled by expansion and the lowered dew point produces fog on the windward slopes of the mountain. No! -you didn't drive through this. - - Note: The high wet appalachians are the foggiest places in the contiguous states. More so than Oregon. I think.



Evaporation fog occurs when a layer of cold air moves over warm water or warm, moist land surfaces. This results in fog formation as the water evaporates into the cold air. This is probably what you saw.

Is there a name for what happens to the fog when you get to an interstate and the fog appears to be divided.
Good heavens I hope not. If we keep on naming each and every thing and forget our adjectives, our mind will become so cluttered it will be like driving down the interstate in... split-pea-soup. - -