Hi Mike, you can use the Delete Identical to specify other fields along with the test for shape. So for example, if lines have identical geometry, but you'd like to keep all the identical shape lines if their distances are different, then add the "Distance" field (and "ArcLength" field) to the Delete Identical field parameter list:
For your historical example, if you have carried over the "Historical" field intact, then you could also use that field in the parameter field list. Then even if all other values and geometry are the same, since "Historical=1" <> "Historical=NULL" (or 0) they would not get removed.
What would be a bit more challenging is if you have lines with the identical distance, but with differing record directions. This is trickier because we know that many truly identical lines will have directions that are 180 degrees different, and so using the Direction field would keep lines that you really wanted to remove. One possible solution to that would be to first create and calculate to a separate field only the decimal portion of the Directions, and then run Delete Identical using that field.
Similar issue for circular arcs and using Radius field, because of the positive/negative radius value.