I got this question today and thought it worth capturing a video of some processes that you can use to model up the Intersection - it doesn’t cover the entire process, more the tools that you can use to create the model
The issue presented is that there is a Main Line Road with Ditch and a Side Ditch coming into the Main Road Ditch - both modeled as Surfaces / Corridors and wanting to create a "Nice Intersection between the two surfaces.
This process uses Surface Intersection Linestring, Null texturing, CAD Tools and a few other tricks to create the intersection of the surfaces.
Hope that this helps