With the release of Civil 3D 2016 Productivity Pack 3 comes a brand new collection of subassembly parts. Included are nearly 30 new components representing a wide range of use cases. This expanded content allows engineers to model even more types of curb, sidewalk, shoulder treatments, daylighting and pipe trenches "out of the box".
That being said, if you'd like to make some changes each new subassembly is provided as a .PKT making them easy to customize using Subassembly Composer. The parts may also be reverse engineered if desired, to simplify the creation of brand new parts.
If you are interested, I've created a quick video that shows how to take advantage of this new content!
(Note: Productivity Pack 3 is a free-of-charge subscription benefit for users of Civil 3D. Instructions for downloading Productivity Pack 3 can be found here)