Bingo!
After quite a bit of searching, I've finally found the pot of gold.

This US government site has copies of maps from the 12th Army Engineering Section, from 6th June onwards.
They show roads, railroads and rivers, and are fully zoomable. These show the major roads across France close to the time we're interested in.
http://memory.loc.gov/ammem/gmdhtml/milhome.html If you are even the least interested in the battlelines from 6th June onwards across northern France, then this site will be a great one to visit.
Don E.
[This message has been edited by Donnybrooke (edited 12-26-2002).]
[This message has been edited by Donnybrooke (edited 12-26-2002).]