Convoys are hell. This is a simple fact.
So don't expect perfect results, or even somewhat-okay results. You'll be disappointed.
However, what I usually do to make it work as smoothly as possible is to make sure the truck drivers are all placed in order of rank. So the one leading the convoy might be a Colonel, the one following a Major etc. all the way down to private. That way, they all follow one another logically.
Also, I'm sure you meant COLUMN formation, not LINE formation - column is when they're all one after the other (in a column), line is when they're all next to each other (in a line).
Safe Mode is also best, that way they'll stick to the road. I must say though, that hoping to get 10 vehicles to move down a road in a nice tidy convoy is pretty much doomed to failure unless you get phenomenally lucky. Maybe making them into two groups or something might make it easier?
Good luck, anyway!
Wolfrug out.