The OP also touched on crowded travel routes. That is something that is a daily occurrence here in SoCal - it is known as "rush hour." If you must travel, try to be a contrarian and find the path less traveled, or get ahead (or, sometimes, behind) the crowd. The measures you need to have in mind vary tremendously depending upon your circumstances. People in Rapid City have a much less severe problem than those in Los Angeles.

I like to include a bicycle in my plans. They can thread through a crowded freeway with ease and take to side roads when necessary.