I started the model with InfraWorks to capture the existing track. I then built the high banked track with Civil 3D Corridors. Exported the Civil 3D model to 3D Studio Max via Civil View then exported to an FBX file format. I also modeled other environment assets with AutoCAD and 3D Studio Max. A workflow is coming soon and maybe to AU2019 if I'm lucky.
Here is the latest progress of the driving SIM recorded from Unity 3D.