Some interesting thoughts on convoys.
http://www.globalsecurity.org/milita...11-43/c5s2.htm
Looking for field manuals is always a good idea because the military has prepared for many situations.
I would say the most important element is Intelligence, followed by speed.
I am not sure about running full bore as roadblocks could lead to all kinds of nasty surprises (concrete pillars, Pits, IEDs, etc). I think you have to clear them as quickly as you can with engineers.
A sitting convoy is in much more jeopardy so I would hope you would see the roadblocks early with an air asset, then send in a suppression team, then engineers.
400 miles will be tough to go in one day IMO so that leads to either traveling at night or setting up a camp overnight, of which I would prefer neither
. I would only do the latter if you have rigorously scouted the area around a potential overnight base.
In regards to laying rail over highways, that is an interesting but IMO WAY too difficult prospect unless it is a very short distance to connect two existing rail lines (perhaps bypassing damage).
You can find rail lines on Google Maps (gray/white lines) but the are most visible at the top four highest zoom levels. Rail is far more efficient if that is an option.