[Tagging] Traffic sign relevant direction: relation type:enforcement vs. direction=* vs. traffic_signals:direction=*

Paul Johnson baloo at ursamundi.org
Fri Mar 31 07:54:43 UTC 2017

On Thu, Mar 30, 2017 at 7:01 AM, Kevin Kenny <kevin.b.kenny+osm at gmail.com>

> On 03/30/2017 07:43 AM, Paul Johnson wrote:
>> On Mon, Mar 27, 2017 at 9:21 AM, Kevin Kenny <kevin.b.kenny+osm at gmail.com
>> <mailto:kevin.b.kenny+osm at gmail.com>> wrote:
>>     Obviously, if we are using the node for other purposes, we may
>>     need to disambiguate with stop:direction=* or
>>     give_way:direction=*, just as we do with other ambiguously-named tags.
>>     I'm having a hard time picturing any case where this couldn't
>>     work. It doesn't involve measuring distances to intersections,
>>     trying to divine from a sign placement beside a way what it means
>>     for traffic on the way, or any other weird preprocessing.
>> Well, every instance where the restriction only applies to one direction,
>> because nodes lack direction.
> Yes. Nodes lack direction. Ways do have direction. Traffic arrives at a
> node along a way. 'direction=*' indicates that the restriction applies to
> any way arriving at the node in the given direction, relative to the way it
> arrived on.
> Did you even read what I wrote earlier?

Yes, however, you're still trying to apply a direction to a node, which is
entirely independent of the way it's attached to and it's direction, and
that's the crux of the problem.  This is exactly the reason why relations
are used to model enforcement objects (speed and red light cameras) and
turn restrictions.
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