A method is disclosed for creating a flattened version of a three-dimensional electrical harness assembly design in a computer-aided design environment. The method includes storing data in computer memory including route segment identifiers, diameters, lengths, and end points for route segments in the electrical harness assembly. A computer processor designates route segments as forming a trunk line of the electrical harness assembly, based on the stored data, and produces a flattened two-dimensional version of the design. All the route segments designated as forming the trunk line are represented in the flattened 2D version by straight connected lines, having a particular orientation (e.g., horizontal), and every other route segment is represented as extending out from the trunk line. The flattened 2D version is displayed on a display screen of a computer.