Service area (from point) or
Service area (from layer) geoprocessing tools create 1 resp. n multipart line features which (usually) contain many overlapping sections.
Most of them can be removed by running
Split with lines (with itself) on the resulting service area layer.
However, overlapping lines remain that can't be removed using
Delete duplicate geometries.
Here's an example of a service area that has been dissolved and split with lines:
All start and end points of the lines have been extracted as vertices here. I selected two vertices that are start or end points but seem to be located in the middle of a network edge because the respective line makes a "180 degree turn" and then partly overlaps itself. The other few cases with (partly) overlapping lines can be visualized using the "Identify feature" tool. In the following screenshot, only one feature is selected, but obviously there is a start or end point of another line located along this edge:
This seems like a bug within the service area or the split with lines tool—-and leads us to the detailed question:
How can these remaining overlaps (self overlaps and short lines overlapping longer lines) be removed in a performant way?
Delete duplicate geometries obviously only works for complete geometries and I have not found another tool yet to solve the issue.
This question came up when working on solutions for the question Extract all dangles of service areas in QGIS.