[OSM-talk] confused about roundabouts and ways

[Simon Hewison]

Andrew Loughhead wrote:
> In previous list discussions I find the recommendation to tag
> roundabouts with junction=roundabout, highway=secondary (for example).
> Thats fine, but I can't see a description of how the ways should be
> constructed.  The previous osm-talk discussions don't specify, but can I 
> assume that we want to tag ways, not segments, even for roundabouts?
> 
> Specifically:
> 
> Is junction=roundabout applied to segments or a ways?

ways. Create a way that goes around the roundabout.

> If there are triangles connecting the roundabout to single carriageway, 
> are the two connecting pieces part of the roundabout way?

No, that would end up with a forking way, which isn't good. It's only really 
worth doing that if the triangle is large enough that someone might get 
confused which exit is an exit, and which is an entrance to the roundabout.

> Lets say the roundabout is a junction of two different classes of road, 
> highway=secondary and highway=unclassified, all four connecting roads 
> are single carriageway, and all four connect to the roundabout with 
> triangles.  The roundabout way would usually want to be 
> highway=secondary. But if the roundabout way includes the triangles of 
> the highway=unclassified road, then the triangles will render as 
> highway=secondary, which will be ugly and misleading.

Typically, cartographers render a roundabout in the style of the highest 
class of road that meets at that roundabout, excluding motorway slip-roads.

> If a road has the same name each side of a roundabout, is each bit a 
> separate way?  Or can they be disconnected parts of a single way?

Side of a roundabout? a roundabout is normally vaguely round.
If it's a roundabout that is in the middle of a street, I create a separate 
way for the roundabout, and then a way either side.

> The editing guidelines say each direction of dual carriageway should be 
> a separate way. If a road alternates between dual carriageway and single 
> carriageway, is each part a separate way?  If so, does this apply to 
> things like roundabout triangles, where the road is briefly dual 
> carriageway?
> 
> Do roundabouts get a name attribute?

Yes, if they are named.

-- 
Simon Hewison