[talk-au] What gives with roundabouts?

Darrin Smith beldin at beldin.org
Thu Dec 11 10:49:49 GMT 2008


On Thu, 11 Dec 2008 19:52:50 +1100
Liz <edodd at billiau.net> wrote:

> I'd like to second Ian's request for more information to be discussed.
> Darrin, could you please put up some photographs of the sort of
> roundabouts you are discussing. We may all agree that they are apples
> in the end.

I'll look through my collection and see what I can dig up that's
clear, I may have to actually go and take photos of some of the ones I
haven't actually been near in the last couple of months since I
started doing the photo thing..(A couple are listed below)
 
> I have put on the wiki some information culled from wikipedia.
> http://wiki.openstreetmap.org/wiki/Roundabouts
> The Germans (in a Germanic way) have the definition down to the metre
> of the Mini, small and large roundabout. The Poms are the odd ones
> out in their definition of the mini-roundabout with the curious
> painted circle on the ground.

Couple of things on that page that don't add up:
German roundabouts are mini from 18m to 25m, what do they call anything
less than 18m? As I said in the previous post I think the Poms were talking more about
a Height issue than a width issue (i.e. painted on the road is zero
height = mini_roundabout). It's possibly a problem of naming as much as
anything (as these things so often are). The again both pictures of
mini roundabouts on the German page also show no raised island in the
middle of the mini roundabout! I don't think the definitions are that
different after all.
Looking at the English Equivalent of that page:

"The centre island also must be able to be over-run by larger vehicles.
If this is not possible, perhaps due to plants, or street furniture it
is considered a small roundabout not a mini roundabout and as such must
adhere to the stricter roundabout guidelines."

Sums things up well I think.
 
> We should not be making up the definitions of these things for OSM.
> We should be using definitions either from RTA (NSW) or Transport SA
> or other local authority. If they don't exist or can't be revealed to
> us then the work of people who write Wikipedia and have the time
> knowledge and inclination to research these definitions should be a
> next resource. If we have access to University Departments of Traffic
> Engineering; Geographic Information Systems or Urban Planning they
> may also be sources of definitions.

Ok, fair enough, even though we've generally snubbed these definitions
in other areas (such as highway classifications) we'll consider it
here? Searching Transports SA's site is as helpful as always (i.e. NOT).
 
> I'm pragmatic about the roundabouts.
> Does putting 4 nodes on the map with a one way loop improve the
> usability of the map?

I've covered this in my previous two posts so I won't bore everyone
with being too repetative ;) However, you are looking at it from
the reverse point of view as did the original discussion.
junction=roundabout is the NORMAL situation, we should be asking does
merging all the nodes and using mini_roundabout improve the usability
of the map?

> Junction=roundabout has been seen mapped onto a single node, and then
> doesn't render in JOSM. It requires at least a few nodes and a way
> drawn in the direction of travel.

Renderers can be changed (with a lot patience according to BlueMM ;).
It really makes more logical sense. 

> I would like to draw the discussion away from the subjective
> "laziness". This immediately draws battle lines and polarises the
> discussion, so that we can't reach any consensus. I have put up
> sample roundabout photos consistent with the Wikipedia English
> definition, and am happy to view others photos and discuss further.

Actually you haven't. The pictures on that page are ALL roundabouts not
minis by the Wikipedia English definition (none of them can be
over-run by large vehicles). What's more none of the are mini's by the
current .au definition, every one of them is wider than the roadway!

Here's one I suspect is very like the one you changed the other night:

http://osm.beldin.org/2008/12/dscf5133.jpg

(And there's another in the background also). Now both of those are
wider than the road with - admittedly only just, but I get the
impression they are considered 'mini' by some, despite the fact they
definitely don't fit the English Wikipedia definition.

Here's another one, again I was more focused on the road signs than the
roundabout so it's not 100% clear...

http://osm.beldin.org/2008/12/dscf5404.jpg

That one's a little bigger, and because the road bulges around it, I
supposed it's not a mini? The current definition makes these ones
exceedingly unclear.

Another of those borderline cases, the road splays out around it and
the island is wider than the road, so I guess it's not mini, but it's
as small as the first one I listed, width definitions don't really work.

http://osm.beldin.org/2008/11/dscf4217.jpg

Finally found one that seems to fit the current definition:

http://osm.beldin.org/2008/11/dscf4526.jpg

The roundabout actually appears to be smaller than the road width, and
I think if they're really luck a bike could go through it straight
without any turning at all ;)

But even so, to make this one different from the other cases around the
place seems a  bit silly to me, they all function the same, they all
break up the road the same, are signed the same, and you have to use
them all the same way.

Here's a bunch more borderline cases by the current definition:

http://osm.beldin.org/2008/11/dscf4816.jpg
http://osm.beldin.org/2008/11/dscf4818.jpg
http://osm.beldin.org/2008/11/dscf4821.jpg
http://osm.beldin.org/2008/11/dscf4826.jpg
http://osm.beldin.org/2008/11/dscf4827.jpg
http://osm.beldin.org/2008/11/dscf4829.jpg

None of these fit the English definition of a mini, but they're almost
exactly like the original ones in question.

Here's an interesting one:

http://osm.beldin.org/2008/11/dscf4872.jpg

Roundabout is definitely smaller than the road width, but it's a
divided road. And if we follow the you can make it a roundabout if you
want idea, then we end up making a smaller roundabout a
junction=roundabout that some of the other cases, kinda defeats the
whole 'mini' idea.

I will endeavour this week to get pictures of the other 2 cases I
mentioned (The genuine Australian mini roundabout and the 2-lanes one
that might just fit the mini definition), one is one my way to work so
I can probably grab it tomorrow, the other might take till early next
week then I'm down that way again, if you're still in Adelaide Liz and
manage to take a drive down (hey or anyone else who's feeling
camera happy!) Gasycone Avenue Hillcrest, there are 3
minis along it and one 'small' at the eastern end of the road.

Also I'm not sure if I made this clear, I'm not against people putting
in mini's on roundabouts really, I just have trouble seeing why
anything but a flat central island with no signage, raised edges,
plants or other street furniture should be reduced to a mini if it's
already a roundabout (and in the long run all such cases should be
upgraded to roundabout, but it's one of those things we've all got
better things to do than ;)

-- 

=b




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