Better search the Manual under:
Manual > Street Networks (then all subtopics)
StreetNetworks create Dynamic Shapes, thus checking the Shapes documentation is not the perfect place.
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You can not automatically 'clean' all tangents in the way you want. There's an infinity of possibilities to do that, thus it's not efficient to try to caltulate this. I've had a quick chat with the developer. The only 'quite efficient' way to get rid of such overlaps would be setting the minimum angle automatted according to my last post, but this would need to be implemented. I'll have to see whether this will get included in the roadmap.
For now, you'll have to clean that manually.
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You can merge double roads by using large radii in the cleanup tool. The docs may enlighten you .. 🙂
Manual > Street Networks > Cleanup Graph