[talk-au] Mapping interchanges levels or turn restrictions

[cam_daw at fastmail.fm]

On Mon, 2010-01-11 at 21:44 +1100, Roy Rankin wrote:
With the resolution and newness of Nearmap images Freeway/Motorway 
> interchanges are being mapped in detail rather than schematically. This 
> brings up the issue on how to best do this.
> 
> ... 
>  
> (http://www.openstreetmap.org/?lat=-33.82907&lon=151.21494&zoom=17&layers=0B00FTF 
> ) The mapper did not realise that ways with turn restrictions must break 
> at the via node. Unfortunately the current tested JOSM does not handle 
> turn restriction relations properly when a way is split and much effort 
> is required to fix up the relations after a way split. As each way had 
> quite a few turn restrictions I realized that after splitting the ways 
> it would require some time to sort out the relations. I thus used method 
> 2 above and deleted all the relations.
> 
> Regards,
> Roy Rankin
> 

Good point there Roy,

This intersection was my doing, I wasn't 100% sure how to do turn
restriction relations that well, and OSM's documentation for straight_on
isn't clear.
http://wiki.openstreetmap.org/wiki/Relation:restriction

That is a particularly messy intersection to deal with:
http://www.openstreetmap.org/?lat=-33.829754&lon=151.214575&zoom=18&layers=B000FTF

Personally I'd prefer to use turn restriction relations rather than just
using different layer tags for these complex intersections, as it seems
to be more the "proper way" of doing it.

After having a look at your handywork fixing up that intersection Roy,
it does indeed make reading the intersection much easier in JOSM.

But indeed as you say, just using layers, one way roads, and some
non-connecting ways is in itself a rather elegant way of doing things.

Would anyone else like to comment?

Regards,
Rhubarb.
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