[talk-au] Join roundabouts

[forster at ozonline.com.au]

Hi

Going a bit off topic, is there anything in the wiki about breaking  
relations, ways they break, what not to do? I am always a bit nervous  
editing members of relations. I guess you repurpose existing elements  
rather than deleting and replacing, but I may be missing subtleties.

Tony

> For larger roundabouts I can see how the roundabout needs to be split and
> the "from" member would be the roundabout segment, for smaller ones I can
> see how the "from" would be the way leading into the roundabout and "to"
> would be the way leading out of the roundabout and there would be no "via",
> depends on the roundabout.
>
> I haven't see anyone intentionally breaking things by merging, so I'd
> strongly recommend to leave friendly changeset comments (if you haven't
> already) because not everyone is on this list and for new contributors and
> even experienced contributors mistakes happen, so changeset comments are
> the best way to try and limit breakage in edits.
>
> On Sat, 4 Apr 2020 at 22:52, Nemanja Bracko (E-Search) via Talk-au <
> talk-au at openstreetmap.org> wrote:
>
>> Hi,
>>
>>
>>
>> We could see that couple of users started joining ways that have an
>> attribute *junction=roundabout* into single way.
>>
>> By doing so, we recognize following (potential) issues:
>>
>>    - We have added plenty of destination relations (overpass query
>>    <https://overpass-turbo.eu/s/SlI>) across Australia, and by joining
>>    roundabout ways into one, relation could be broken because members “from”
>>    are lost. In the same time, “intersecting” members haven’t been added, so
>>    the relation is invalid;
>>    - If lanes (in real life) are changed within the roundabout (usually 2
>>    lanes at some parts of the roundabout and 1 lane at the other),   
>> attributes
>>    regarding lane information are lost;
>>    - Route relations could also be broken;
>>    - If junctions are NOT roundabouts (but have a circular/elliptical
>>    shape), and ref id’s were correctly set, after joining ways, refs would
>>    probably miss or just one would be present.
>>
>>
>>
>> Some examples:
>>
>> https://www.openstreetmap.org/way/717778304
>>
>> https://www.openstreetmap.org/way/39804616
>>
>> https://www.openstreetmap.org/way/717765311 - travaudat actually added
>> “intersecting” role, but it is clear that lanes are changed within the
>> roundabout
>>
>>
>>
>> I would ask users to try not to brake existing relations, and to note that
>> multiple ways can be a part of single roundabout so it is not necessary to
>> join these.
>>
>>
>>
>> Thank you,
>>
>> Nemanja
>>
>>
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>