[OSM-talk] Turn restrictions ambiguity

[Tobias Knerr]

SteveC wrote:
> On 23 Apr 2009, at 12:17, Teemu Koskinen wrote:
>> If both from and to ways continue after the via point and neither is  
>> one-way, there's two possible ways to interpret it: the restriction  
>> could apply when coming from either of the ends of the from-way.  
>> This of course doesn't matter if there is similar restriction coming  
>> from both directions, but that's not nearly always the case. And  
>> even if there is symmetry in the real life restrictions, it's not  
>> appropriate in my opinion to map those with just one restriction.
> 
> eh? don't you assign direction by saying 'from' and 'to' ?

       |A
       |
       |
      x|     B
-------*------
       |
       |
       |

Imagine this situation, ways A and B with a common node x. You are
moving on A from north to south and are not allowed to turn into B. If
you create a restriction "no_left_turn from A to B via x", you will also
prevent that cars moving from south to north on A can turn left. This is
usually not intended.

Tobias Knerr