This is going to get real easy or real sticky depending on where you want to go with it. I just finished country wide road networks for my new project.
Easy.
Click on the paths tab and click on the create all paths. You will have choices for creating the active convoy roads then do it again for the active train resupply tracks. Then go look at every airfield, vbase, port and strat. You will have an east running straight line 10 miles long of road at feilds and tracks at strat. Now you get to move them around a bit to conform to the terrain. The tool tips will tell you how to manipulate the segments. Just make sure after you manipulate the road or track that it is 10 miles long. It is OK to stretch, add or delete segments to achieve 10 miles. Just make sure at the end that stops next to the destination that it is 1\2 of a 660ft square away from touching the square object boarder edge. You can see this if you push your view down onto the ground and go to wire frame view. Don't change anything in the properties menu for any of those roads and tracks.
When you have all these manipulated into place, run the error check and you will see it say you need to run the mask. That option is above build. Run the mask and go get some coffee or do your laundry. It removes trees and bushes and clutter from the roads and tracks. And from rivers if you put any in. When it's done run error check again, if all is OK, run build. Then go offline, wait 10 minutes, and you should see convoys and trains running. Then a new one will spawn every 10 minutes and run after that.
Sticky,
You want to add in a dummy road network and run roads over bridges. It will drive you nuts.......
This small snap shot of the three country road network with bridges over rivers took a month and was a pain in the paducka. I won't know until after the terrain is in rotation if it was even worth doing. I think Hitech has some things he still has to tinker with on the river paths before this terrain can be considered for rotation. Waffle didn't paint a road bed up the berms on each end of the bridges so you have to run a dummy road up at an angle and adjust heights with several nodes to get just the surface to show or the road shoulder can tip over tanks climbing up to the bridge road bed. If it is an active convoy road you have to run a segment over the bridge bed and set it to not be visible. Sticky and irritating fussy work.