Well, for those DOT engineers out there that won’t move from Microstation, [not mentioning any names (TXDOT)], you can now move freely between Civil 3D and Microstation. This can be achieved by using the Autodesk Civil Engineering Data Translator 2015 extension.
This extension requires an Autodesk 360 account. The extension is stored and executed from the Toolbox in the Toolspace in Civil 3D. You can download the extension from the Autodesk Subscription Center.
For more information and related tasks, visit the knowledge base here.