Hello,
First, I essentially have the same problem as described in this person's post and would really like to get an answer.
https://communities.bentley.com/products/road___site_design/f/geopak-inroads-mx-openroads-forum/196435/conceptstation-to-openroads-designer---sight-visibility-tools-workflow#
I am trying to export my file from OpenRoads to Rhino but everytime we try, the 3D elements are not correctly exported. The file becomes 2-D. We have tried various types of files type, converting to b-spline surface, and all doesn't work. The issue seems to be that when we export from ConceptStation, everything gets converted to extended elements. We turned everything into mesh itself, and tried to convert the mesh to a solid and volume, but nothing work. Has anyone else encountered this problem and how did you solve it?
Maybe try the command MeshUnite, to unite the differebt roads parts, then maybe CloseMeshVoid then maybe it will works? But I don't think ther is an easy way or just a way to convert mesh to solids in a way that Rhino will read them well. I know there are some third party program for civil 3D that convert polyface Mesh to Solids, maybe this will work. The thing is I don't have Rhino to test it.