Driving in fog, both heavy and light, can be extremely treacherous. It is important to be aware of safe-driving best-practices in instances of fog. Knowing what to do and how to react in advance might just save your life.
Immediately driving slow and steady is the first important rule to follow. Keep a safe distance between your vehicle and the one in front of you.
A map has such small print, it's impossible to safely read it while driving. If you are needing to find a specific address, write out the basic directions in large writing and short sentences, before you drive there. If you must read the directions (not the map) while on the road, do it where you are stopped.