Studies show that some drivers acclimate themselves to foggy conditions and unconsciously increase their speed over time. Make sure that you can be seen. Turn on your fog lights, and make sure your high beams aren't turned on by accident. High beams direct light up into the fog, making it difficult for you to see. Low beams direct light down onto the road and help other drivers to see you.
Most European cars have a switch that turns on extra-bright auxillary rear fog lamps.
American and Asian vehicles lack this important safety feature. Don't use your emergency flasher. Studies have shown that drivers are attracted to flashing lights and tend to drive into them inadvertently . Whatever you do, don't turn off your headlights in heavy fog, even if they interfere with your forward visibility a little. Headlights are the only part of your vehicle that oncoming drivers can see at a distance.