[Tagging] Another reset on roundabouts

Toby Murray toby.murray at gmail.com
Fri May 18 05:19:19 BST 2012

On Thu, May 17, 2012 at 8:59 PM, Andrew Errington <erringtona at gmail.com> wrote:
> On Fri, May 18, 2012 at 7:21 AM, Toby Murray <toby.murray at gmail.com> wrote:
>> Otherwise we can pontificate all we want on the mailing list but
>> people who are not familiar with the concept of a "real"
>> mini-roundabout WILL still use this tag for "small roundabouts" with
>> non-traversable centers. That's just reality. Maybe change the display
>> label to "traversable roundabout" or something?
> If the definition is clear in the wiki then there should be no
> problem.  Anyone discovering something in the database that does not
> match the definition is free to correct it.

By all means, make the wiki crystal clear. But how many of the mappers
who have added mini roundabouts outside of the UK do you think checked
the wiki before they tagged a node? 1%? No. They saw the preset in
their editor (both JOSM and P2 have one) and clicked on it. That's
what I did. I had no idea there was such a thing as a "mini
roundabout" that met strict requirements until months after tagging
several intersections in my city as such. And I am not a casual

> In real life the definition is quite clear.

Only to people who actually know what a mini roundabout is.

> We have two distinct nouns, 'roundabout' and 'mini-roundabout'.
> Although 'mini-roundabout' is made from two words which have a
> well-understood meaning, the compound word has its own specific
> meaning.  Adding a further definition (such as 'traversable
> roundabout') is not necessary, since, by definition, a mini-roundabout
> is traversable, and a roundabout is not.

Ask anyone who has never seen a true mini roundabout. I guarantee
their response will be "oh it's a small roundabout." I'm not saying
you are wrong. I'm saying without further clarification the definition
of a mini roundabout in OSM will be worthless because people WILL use
it for things that are not true mini roundabouts. So either we accept
that the definition will change based on region or we have to present
it to the user differently.

> 'Roundabout' on a node means this is a
> small roundabout, but it was too much effort (or too tedious) to draw
> a circular way.  It is not traversable, and traffic must 'go around'
> it based on the local rules for direction and giving way.  Anyone who
> discovers 'roundabout' on a node is free to re-draw it as a small
> circular way.  The net effect to routing should be negligible.

I agree with this. It's just that the JOSM validator complains to high
heaven if you put junction=roundabout on a node and P2 doesn't offer
it as an option when you have a node selected. Oh but what's this I
see in the presets? A mini roundabout? Oh, that's perfect! I'll use
that instead.

> I think the problem is that we use 'mini-roundabout' with highway=*
> and 'roundabout' with junction=*.  In my opinion they should both be
> junction=*, with 'mini-roundabout' restricted to nodes, and
> 'roundabout' applicable to nodes or circular ways.  Furthermore, when
> applied to a node we should probably encourage the tag direction=*
> although some software can probably figure that out.

I have no problem with this either although if history is any
indicator, changing tags that are actually in use is nearly impossible
so good luck with that.

Again, I'm not saying you are wrong on how things SHOULD be. I'm just
pointing out that your view is skewed by the fact that you know such a
thing as a mini roundabout exists in real life.


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