Problem: Construct Features Command Polygon to Line creates duplicate lines for adjacent polygons
When editing in ArcMap, you can use the Construct Features command to build new polygons or polylines from existing features and store them in the target layer.
However, when using Construct Features to construct lines using selected polygons that are adjacent to one another, the command will create duplicate lines in the target layer.
The Construct Features command does not consider coincident lines when creating new features.
Solution or Workaround
Use the Planarize lines command after constructing the new line features. Planarize will remove duplicate lines.