[Tagging] Proper Tag for Not-a-Roundabout

Tom Pfeifer t.pfeifer at computer.org
Fri Nov 18 19:14:23 UTC 2016

We had plenty of discussion over three days, unfortunately without a 
resolution. We were discussing specific roundabouts, and what the best 
router announcements would be in various cases. We did not decide about 
a value.

Currently, OSM defines junction=roundabout with two conditions 
fulfilled, i.e. going round a non-traversable island AND circular 
traffic has right of way (when potential traffic lights are off)

Nobody objected the idea to assign a 'junction=' tag to installations 
that fail the OSM definition above, in particular with different 
right-of-way situations (all ore some incoming roads have priority). The 
only objection was against "not-something" troll tagging.

So far we had on the table, with taginfo in brackets:

1 junction=circular (0)
2 junction=circular_crossing (0)
3 junction=circular_junction (0)
4 junction=traffic_circle  (35)

For comparison, junction=roundabout (429490)

My strong preference goes for 1 "junction=circular", as it is concise, 
has not a biased meaning towards the roundabout-definition, and is 
highly descriptive, namely a junction that is circular. Thanks Martin 
for proposing.

2 does not fit so well as we have no crossing. 3 duplicates the term 
'junction' in the value, we have that in the key already.
4 'junction=traffic_circle' is the N-Amer synonym for BrE roundabout, 
thus might be ambiguous. The 35 current uses need to be ground-checked 
what they label.

The definition for the new value needs to restrict the size a bit, e.g. 
not having other roads inside the circular junction. Thus we would 
exclude e.g. the motorway ring around a city.

Please note that we are just discussing the _tagging_ here. The routers 
and renderers can still use it as they like, and I still do not like 
announcing exit numbers on a large roundabout/circular junction.

On 07.11.2016 15:30, Daniel Hofmann wrote:
> 4/ Not-a-Roundabout (what this post is about)
> There are situations where one of the entering road has right of way,
> which disqualifies the scenario for being classified as a roundabout.
> The Wiki has a section on these Not-a-Roundabouts:

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