Here is a little-known feature in AutoCAD Civil 3D I discovered by accident. It works back at least as far as version 2010, and probably further.
When you create a top surface for a corridor, the Curb triangulation can go haywire where you have very close Frequency lines in the corridor, as happens frequently at the edge of intersections.
These can be fixed by manually swapping surface edges one by one, but more useful is to add the feature lines of the Curb as additional parts of the corridor surface definition (see the image again). Then they become automatic breaklines. What's more, they are dynamic so as the corridor moves and changes, so do the breaklines. Easy!
Just make sure the first part of the corridor surface definition is the top links and the Curb Featurelines are listed subsequently.
Note: This Civil 3D tip has not been reviewed by a Cadalyst tip reviewer.