[OSM-talk] Crossing ways

Jon Bright jon at siliconcircus.com
Sat Aug 11 17:49:26 BST 2007

Hi Mike,

Mike Collinson wrote:
> Looking at http://discord.ensued.net/crossingways1.png, I'd expect to
> see the minor road physically divide into three divide into three link
> roads if I drove along it, two of which (implicitly) cross the dual
> carriageway by bridge or tunnel. I suspect, forgive me if I am wrong,
> that instead you are trying to model the logical arrangement dictated by
> traffic lights and signs to show that U-turns are not allowed? I don't
> think you can do that with the current OSM model; as indeed you suggest,
> some sort of extra tagging would be required.

It actually does split into three (you could even regard it as four). 
Here's a Google Maps link:


(You might notice that the dual carriageway there doesn't actually have 
a median/barrier - but there's a solid white line along the middle of 
the whole stretch, U-Turns are forbidden - and would be near-suicidal 
for most of the day - and the whole thing is basically a 
dual-carriageway without a barrier.  The street on the opposite side, I 
haven't mapped yet.)

> Assuming the real physical layout of the junction is simple (?), I
> personally just show the minor road connecting to a node on the nearest
> carriageway and carrying on to finish as a node on the second
> carriageway. 

David Earl suggested that in another mail, which I'm just about to send 
a reply to, so I'll leave it for that reply.


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