It's actually extremely easy.
You came to a forum for advice, and it don't seem it but this... is top notch advice:
Stare at R*'s nodes for ages. Maybe 2 hours. Until you understand how that node... connects to that node.
And also, there's 3 main areas to me. The world placement of the node, which is not very important and doesn't have any limitations, in my view. The "link" tab between each node, and the most important thing is understanding junctions. They are insane, well, they're not, but they look it. Basically, R*'s developer tools enabled them to build these files that the game uses for proper wheel-road matching, whereas we peasents only get to create heightmaps through hours of transforming flat plane after flat plane to blender and back again. Here's my second tip, just use the visual heightmaps for junctions copied over. Making a 4 way junction with only 2 sets of traffic lights and 1 left-hand only turn lane? Find it! And copy it!
1 more thing I can be bothered to type right now, is that the biggest bug I've come across is the area node crossover thingy glitch. Basically, you have area IDs right? well you see how they are numbered, and inside of them the nodes are numbered too? Well get this shit...
If you got node777.ynd, and node420 linked via 2 fwd-lane links to a node inside 778.ynd called node1 Vehicles going along 777 in the proposed direction will either randomly attempt a u-turn and go through a solid, like a wall/ building, or just turn around and attempt to drive the other way. Second bug is boring. Why is the first bug interesting? Cos what happends is the AI attempts to go to node1, which it should, but it is referencing within itself and not transitioning to area ID node420.ynd. Therefor, the car randomly drives through a solid and literally flys back to the start of that area node, node1.
Anyone reading that's tried my Re-Roading project would have seen this. Supppper easy to fix. Hands hurt will update if you run into this haha
thanks for your contribs fam