By Graham Riddleston
One thing that frustrates several new users when creating corridors if that the default frequency for applying assemblies is set quite high so the user has to change the frequencies in the corridor properties :
This can easily be solved by selecting the Settings Tab in Civil 3D Toolspace and navigating to Corridor > Commands > CreateCorridor then right click > Edit Command Settings:
Expand the ‘Assembly Insertion Defaults’ property and set the desired intervals and click OK
All new corridors will now use these intervals.
See also: Civil 3D 2016 - Corridor Assembly Frequency - Advanced Features