A polyline layer's (green) length is being calculated via $length. Result: ~100 meters (EPSG 31466).
A buffer of 5meters is created and via Voronoi Polygons (and several other steps) a centerline is created (red). Result: ~ 200 meters (EPSG 31466).
That simply makes no sense at all if you look at the screenshot. It rather should be arround 110 meters, estimated visually. I tried merging all segments but the result stays about the same.
The background behind this situation is a sum length completeness comparism of two road networks. Because of many withstanding end pieces I want to calculate a factor I can use to divide a total network length with in order to correct the centerline length.