My BP setup uses 2 meshes for the road; one for the cross section(3way) the other for straight road. The sidewalks are also separate meshes. I had made the fence BP suggestion since you mentioned a city and that technique would work for most situations but not all. As you found out it wont work for elevated surfaces so using a spline component is the way to go. You can still make it customizable so it’s fine.
And here is the tutorial i mentioned: [TUTORIAL] Create a procedural spline road tool in blueprints 4 part video series - Community Content, Tools and Tutorials - Unreal Engine Forums