Since Civil 3D is a dynamic model platform it makes designing easier. I think that even more important than that is it’s power as a revision tool. Getting a design idea down is one thing, but as more information comes in changes are inevitable. Or, you might be tasked with creating different options for the design. The ability to create a several options, or try some ideas out on-the-fly, can free up your design to be the best it can be.
If you aren’t familiar with some of the tools that make this possible, here are some highlights.
Alignments + Surface = Profile. And that equation is dynamic, so when you make a shift to an alignment the profile updates. This is the easy one to point out, but it makes all the difference. I remember dreading the 11th hour changes to a design because of the time it would take to make everything work again. You can also create another alignment for options 1, 2, and 3, then quickly apply them to the corridor to see how your design would change. You haven’t “moved” anything so you could easily go back to the design that best fits the direction you need to go.
Data Shortcuts. They are the ultimate in copying tools. You can open up three or four (or thirty) files as different design options and reference in data shortcuts for the existing ground, alignments, profiles, and pipes (especially existing pipe systems!). Then try the different options out in more protected environments. You could even share the options back to the project if needed.
Alignments + Profiles + Assemblies (and + existing ground) = corridors. If you are trying to balance a corridor design there are tools that will allow iterative options throughout your design. Recently added was the profile hatch option which can graphically highlight where a little too much cut or fill is occurring. Also, returning to the dynamic relationship, if you change the profile a little here or there, the corridor rebuilds to show the consequences.
Grading from corridor objects. Mathematically, it is more precise to grade to your slope intercept then what the Daylight tools can provide. It may be a technicality, but grading better represents going around a curve. You can export the edges of your road design as Grading Feature lines, which can be dynamically linked to the corridor, and graded from. If the profile or alignment moves, and changes the position of the corridor, the grading updates with the change.