Before the discussion: I previously posted it under another discussion, but I feel urged to share it more openly with all of you.

I was also troubled by the connection between CSUR/CSUE urban express roads and vanilla highways.

Fortunately, I have personally found a makeshift solution right in the workshop. Here I strongly recommend you all to use SimoG's assets: Highways over Wall .
This series of customized highways can be perfectly compatible with CSUR urban expressways.
Link here: Highways over Wall Complete Collection

Because if you connect CSUR two-way expressway roads with HoW two-way highways, horrible things such as torn decals and modeling will no longer happen.
As a set of "real highways," Highways over Wall come up as a perfect remedy for CSUR, as the latter is not to be recognized by the game's simulation AI as "highway", which causes plenty of flaws of unreality in the simulation of cims' traffic behaviors. Combining the two, you can use HoW for highways and CSUR for urban expressways, e.g., Hangang Expressway or typical Chinese urban elevated expressways.

The only drawback of this solution will be a large consumption of your PC's RAM lol.