This is a sore spot for me with InRoads and Storm & Sanitary - there was never any good documentation for this, except for the actual comments in the istructures.dat file (ASCII) delivered with the product. Here are some links to threads on this:
communities.bentley.com/.../120378
communities.bentley.com/.../76361
You will note that I either started these or added my own answers/suggestions.
communities.bentley.com/.../120378
communities.bentley.com/.../76361
You will note that I either started these or added my own answers/suggestions.