Snippet from the Autodesk web site.
You can use the Autodesk® Civil Engineering Data Translator 2015 extension to translate AutoCAD® Civil 3D® files to files that can be used in Bentley® GEOPAK® and Bentley® InRoads®, and to translate GEOPAK and InRoads files to files that can be used in AutoCAD Civil 3D.
The commands for the Autodesk Civil Engineering Data Translator are available in the AutoCAD Civil 3D Toolbox.
The Autodesk Civil Engineering Data Translator requires an Autodesk® 360 account and an Internet connection. If you do not have an Autodesk 360 account, you can create one when the Autodesk 360 log in dialog box is displayed when you run a translation command, or you can go to www.autodesk.com/launch-a360 to create an account.
How to get the translator. Login to the Subscription Center and click on Downloads, then Product Enhancements on the left side of the page. Search for Productivity Tools for Autodesk AutoCAD Civil 3D 2015
The help file for the Autodesk Civil Engineering Data Translator
A brief description of all the Productivity_Tools_for_AutoCAD__Civil_3D__20152 pdf