"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
The really dangerous part about the valley fog is that it is variable and can change suddenly from 1/4 mile visibility to 0....that is when these pile-ups occur.
These huge pile ups have been happening for many years. Trouble is, one cannot know what to do when they run into a fog bank, slow down, drive off the road and stop, maintain speed? Any choice opens one up to a serious collision. A fix would be to promulgate a rule among all drivers as to what to do when encountering a fog bank. Stopping until it cleared up seems like a good idea.