IMHO, there are too many factors that could affect any true answer to your question. Factors like terrain, climate, how bad off people are, and how widespread the problem is.
I personally think that during the initial SHTF situation, the ill prepared will tend to migrate towards larger towns and cities since the general sentiment would be that's where help and resources are going to be and for a local area SHTF, they're probably right.
If/when things get bad in the cities, I believe people will tend to try and travel major highways and, probably, heading south (depending on time of year) with considerations towards safety, water, and food.
Some will take the roads less traveled probably thinking there will be more resources due to fewer people. Either way, I think most will travel in groups for safety in numbers, if for nothing else.
For me, living in a northern climate, the test will be surviving until the late fall. By that time, food resources are getting scarce and dropping temperatures will make it harder for people to stay warm and sheltered. By then, most unprepared people will be well on their way south to a warmer climate.
