[OSM-talk] Roundabouts and routing

[David Earl]

On 08/09/2011 20:27, Tom Hughes wrote:
> On 08/09/11 19:48, Thomas Davie wrote:
>
>> 1) Don't tag sliproads onto roundabouts as junction=roundabout, instead
>> use some other tagging scheme. Not greatly desirable because it involves
>> a *whole* lot of retagging.
>
> Well who on earth is doing that? and why?
>
> I've certainly never tagged roads entering a roundabout in that way, nor
> can I see any reason to do so.

In areas where it has been important for me (where I've been producing a 
high quality paper map), I have tagged these as junction=approach.

The reason I needed such a tag was to avoid one way arrows cluttering up 
the map on those little Y-shaped approaches to roundabouts; there isn't 
any easy way to tell the difference from a genuinely one way street 
otherwise, but one way markers on these short, often invisible roads 
(invisible because at map scale, they tend to merge together when widths 
are exaggerated).

The problem is exacerbated because many of these were done as a single 
one way which comes off the roundabout and then turns almost 180 deg. 
and rejoins roundabout.

Example:
   http://www.openstreetmap.org/browse/way/4565106

BTW, I don't consider this is "tagging for the renderer" at all. It is 
identify a particular kind of feature that is not otherwise easy or 
possible to identify without specific tagging.

David