[Tagging] Conditional restrictions accepted – turn restrictions ahead?

Colin Smale colin.smale at xs4all.nl
Tue Oct 16 17:30:57 GMT 2012

On 16/10/2012 17:45, Rob Nickerson wrote:
> Hi Eckhart,
> Your right, voting has come to an end for the Conditional Restrictions 
> proposal, which was approved. A statement was not made on this list as 
> Ole and I are working on how best to write the feature page so that 
> some of the concerns raised (about complexity / difficulty to 
> understand) are reduced as much as possible.
> Like Martin, I'm not hugely convinced about the need for complicated 
> turn restrictions (most of the restrictions will be on the road and 
> the detail on the turn sign will simply be advanced warning for the 
> driver). Having said that, you have provided a few examples so I have 
> looked into it:
>   1. Currently we tag a no left turn restriction using "restriction = 
> no_left_turn".
>   2. If we want this to apply only to HGVs then the key is changed so 
> that it become "restriction:hgv =no_left_turn".
> To draw the comparison with "Conditional Restrictions" the above tags 
> cover of <restriction type>, <transportation mode> and the tag value. 
> There is no need to specify <direction> as this is already captured in 
> the relation (from, via, to).
I am not sure you can say this. It should work where the junction angles 
are close to 90 degrees, but for a shallow "Y" junction things might 
need a hint as to whether it is a curve to the right with a junction to 
the left, or a curve to the left with a junction to the right. The type 
of restriction should reflect the road signs. At a T-junction, a 
mandatory left turn could be considered different to a no right turn, 
even if they are effectively the same thing. This cannot be derived from 
the geometry alone.


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