XOIO has shared a two-part video tutorial showing how you can cut roads into a terrain.
The first video discusses how you can create a continuous terrain that features realistic roads cut through steep terrains that maintains edge loops to make the roads easier to texture. Using that workflow, you can even cut roads into steep terrains and create serpentines and mountain streets.
So, you now have the basic topology, and the second part will tell you how you can benefit from the mesh created and texture, refine and animate your scene based on that topology.
Make sure to discuss the guide in the comments.