OK, lets clear a few things up: In fog, you have no control over the actions of the driver behind, therefore it's in your interest to help them out as much as possible. If you can see the vehicle behind you NOT just the lights - then they can see you - so no need for the Christmas decorations to be in full swing. If you leave your rear fogs on, there is a very real chance that the driver behind may not see your brake lights coming on, bear in mind that some drivers don't pay attention at the best of times..... Stopping distances? Sorry, that's almost an irrelevance in this situation as you have no control over how close the car behind you is going to be. Also, the dimmer members of the driving community will hang on to the vehicle in front in heavy fog. Regarding your comment about maintaining the correct distance and not being able to dazzle/be dazzled - sorry, but that is an idealistic situation. BTW, for assessing your own distance from the car in front, the Two Second Rule is much more efficient than trying to assess some abstract measurement. Don't forget to double it in the wet. Could you tell me the correct distance for heavy traffic speeding up and slowing down between 5 and 20mph? There isn't one on the HC..... Heavy traffic will inevetibly bunch up at some point, reducing safety bubbles around vehicles. Add in drizzle, fog and poorly managed foglights into the mix and cars can and will start bouncing off each other. Or, at best, you'll get pished off with the car in front for blinding you and the driver behind will not be your friend for doing the same to him/her...... Plan ahead and drive safe, folks.