Question:

How do you create a terrain model depicting the differences between two surfaces?  This was accomplished using the Isopach Surface in the native InRoads explorer but is there an equivalent OpenRoads tool?

Answer:

The tool used for the Terrain Modeling to create a difference between surfaces is the 'Create Delta Terrain Model' option.  This works similar to the Create Isopach Surface command as it will compare two terrain models and output a new Terrain Model consisting of elevations derived between the two selected terrains.  Please view this video for a demonstration on the Create Delta Terrain Model tool.

http://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/26437.video-create-delta-terrain-model