Does look like a bowtie indeed 
and thought of the logically following⌠junction=bowtie_roundabout, except physically not there, a complete misrepresentation. Leaning to untie this one and restore the prior art.
(Surely there must have been competitions to see who can do the 5 in 1 âmagicâ circuit the quickest.)
Iâve borrowed the bowtie description from somewhere, just not sure where. I thought it was the Mapbox suggestions for mapping intersections but they compare dual carriageways done in this manner to sausages instead. I think itâs geometry we should avoid if possible as it doesnât really represent the layout or how the vehicles move in a meaningful way.
I you look at it as 5 small roundabouts with short but regular ways in between, it doesnât seem that comlicted to me. The whole thing is not a roundabout for OSM, because roundabouts are implicitly oneway traffic. Complicated is: mixing a separate way approach with a lanes approach.
I think the separate way approach (including a circlular way on the roundabouts instead of a centre point) would give the most realistic result, resembling the aerial view and the announcement signs. I wouldnât mind having a go, thereâs just one thing: driving on the left is very counter-intuitive for me, I am bound to make stupid errors because of that. The effect on navigation instructions, I can not predict. Iâm wondering if the instructions and announcement make any sense as it is?
I think this is all essentially correct, the issue with mapping it that way is that they are mini-roundabouts and we currently map those as single nodes. This is why I mentioned it on this thread as something that could be improved by us allowing circular ways for mini roundabouts. As far as editing it, Iâve thought about it a few times and even drafted something once, but the mini roundabout as way issue, the intimidating number of relations going through it and the thought that I might annoy a mapper who actually uses it have all put me off.
Iâm unsure whether junction=roundabout+roundabout=mini_roundabout or junction=mini_roundabout is better. The first pair of tags would allow existing routers to get things right 90% of the time, but may lead to situations where an unaware router encourages a U-turn on the mini roundabout which is discouraged (at least in the UK). The latter breaks things for routers who donât understand the tag, but avoids diluting the meaning of the main roundabout tag.
In places where thereâs a legal difference between mini and non-mini roundabouts designation=mini_roundabout might be appropriate if we used the roundabout=mini_roundabout method.
MRâs are UK only I think?
So far, I have only compared the legal situation of GB and Germany. The only real legal difference between a roundabout and a mini-roundabout in GB is the traffic sign and the white inner circle that identify a mini-roundabout as such. Normal roundabouts in the UK usually have normal right of way signs and/or road markings.
Apart from that, the same road traffic rules apply in the UK as for normal roundabouts, they are only listed separately and explicitly because more specific things have to be observed in relation to the often really small diameter in the UK. The mini-roundabouts in the Road Traffic Regulations are therefore only a sub-item in the section on roundabouts.
Often - resolutely - put forward arguments such as:
are, in my opinion, not reflected in the British road traffic regulations in such absolute terms.
All vehicles MUST pass round the central markings except large vehicles which are physically incapable of doing so. Remember, there is less space to manoeuvre and less time to signal. Avoid making U-turns at mini-roundabouts. Beware of others doing this.
The âfactâ that british drivers would expect different turning instructions has already been described differently here by a british driver in the UK:
Note that historically, when the British invented the mini-roundabout, these mini-roundabouts were really mostly very small and replaced normal equal-ranking intersections. Mini-roundabouts with a central island that can be driven over have now triumphed all over the world, although outside the UK this may be differentiated in traffic regulations.
Even if the really small mini-roundabouts still predominate today, the building regulations have also changed in GB in the meantime. Mini-roundabouts (newly built) in GB can have an outer diameter of up to 28 m. This is actually larger than roundabouts. This is actually larger than roundabouts in Germany, which are considered âmini-roundaboutsâ in construction terms.
And these larger mini-roundabouts already exist!
Therefore, I think it may also be important to the British to map larger mini-roundabouts in OSM as circles and still not lose the important information that the inner circle can be driven over.
translated by Deepl
I think the REAL problem here is that the description of the both just has the traversable center as the difference. So mappers wrongly assume that everything with a traverseable center is a mini_roundabout which it is not.
We need to fix these issues in the wiki.
Flo
On mapping the junction as a node or as a circle: I ask myself, if a split road (two carriageways) crosses another split road, where the junction area in fact is one undivided surface, would I put a junction node in the centre and connect all the carriageways to it?
They certainly exist in France.
Maybe we need a roundabout tool that could replace a mini-roundabout with roundabout (and the other way round), keeping the relations intact?
After all, these relations have some entry and some exit from junction, so it should be possible to connect themâŚ
That would be nice, but in JOSM itâs not that hard to correct the relations. I think itâs more important to agree on when to do it and when not to do it. Maybe the presence of flare islands coud be decisive: if you donât split at least one of the ways, there is IMO no point in using a junction=roundabout circle instead of a highway=mini_roundabout node.
I tried to make sense of the French rules for rondpoints et carrefours Ă sens giratoire, but failed miserablyâŚ
Looked like only carrefours Ă sens giratoire are roundabouts for OSM, and there is no particular size limit for these roundabouts. While rondpoints are not roundabouts for OSM because there is no priority for traffic on the circle. So they are not OSM mini_roundabouts either. Correct?
PS I looked at this one which has no roundabout sign at all, which means it is neither a rondpoint nor a carrefour Ă sens giratoire, I think? Just a slight traffic calming bump on the road.
PS2 Ah excusez⌠I had another look. At quite a distance from the junction, there are warning signs.
But these things are independent. The tool would, first of all, identify all relations needing care after changing. Then fix relations automatically.
Redefining when to use which tagging has less impact on thatbhypothetical tool than deciding on actual tagging (do we keep current concept or define some common tagging for both?)
OTOH, your question might need answer before or paralelly with decision on taggingâŚ
I believe we are talking about existing tagging: roundabout tagging applied to a mini-roundabout (which is a roundabout, after all). I think that is an option if at least one of the roads is a dual carriageway road, e.g. because of at least one flare island separating the approach and exit lanes.
Island,
I think for most mini_roundabouts I wouldnât bother to split the road for a small flare island, in which case I wouldnât map it as a regular roundabout.
A tool might be nice. Identifying the affected relations seems easy. Then of course you have the two main approaches to mapping a roundabout: as one circular way, or split into sections. The first approach might be automated; it could add the ring, put nodes at all the ring crossings, then remove the center node. This will remove the way segments from the center node to the ring causing a break in the relations. The ring way could then be inserted where the break is. Or the other way around: first adapt the relations, then remove the center node and the âspokesâ of the new wheel.
Mapping a roundabout with cut-up ways: how would a tool know what to do with ways, nodes, splitting, geometry?
I could imagine a tool laying down a model roundabout for N split roads, which the user would subsequently fit in, but I donât think that would help me much. I would rather rearrange the existing ways, keeping the tags as they are.
Repairing the damage to the relations would require knowing the intended routes. Maybe itâs a matter of just removing all the roundabout way sections from the relations, then apply a simple routing algorithm to fill in the gaps.
Just speculating, I imagine a lot of experts now giggling at my deep thoughts⌠
I think that âroundabout=miniâ is better for two main reasons.
Edit: spelled wrong tag, now corrected.
be carefull!
junction=roundabout implies oneway=yes and the right of way for the circle.
junction=mini_roundabout would be junction=unknown for most routers and this would not imply anything until it is implemented!
It is important that tagging of mini-roundabouts tells routers that it is a mini-roundabout so that they know not route a U turn.
Which is totally correct for the mini_roundabout as well.
For turbo roundabouts we tag junction=roundabout, roundabout=turbo.
Whatâs wrong with them? I mapped a zillion turbo roundabouts, so I would like to know!
Someone said the legality of that is questionnable?
To make it more clear - The mini roundabout is more of a simple crossing in British Road Laws, made for junctions with equal priority.
In the UK you give priority to traffic from the right, same as a roundabout. It is not equal priority.
Same as a 4 way stop in the US.
Certainly not the same as a 4 way stop.
I first encountered 4 way stops in Canada over 40 years ago and remember thinking these should be mini roundabouts.
