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<p>On a node, traffic_signals:direction=* applies only to the
traffic signals while direction=* applies to all other tags which
may be associated with a direction (camera...). This is the
additional meaning. Let say that traffic_signals:direction=* is a
more explicit tag than direction=* (see <a
href="https://wiki.openstreetmap.org/wiki/Namespace">https://wiki.openstreetmap.org/wiki/Namespace</a>).<br>
</p>
<p>So why is there such a gap in use of the two keys between stop,
give ways and traffic lights? For me several reasons:</p>
<ol>
<li>Because of the wiki. Some people (including me) look at the
wiki as guidelines when mapping (not only as a documentation):</li>
<ol>
<li><a
href="https://wiki.openstreetmap.org/wiki/Tag:highway%3Dtraffic_signals">https://wiki.openstreetmap.org/wiki/Tag:highway%3Dtraffic_signals</a>
encourages traffic_signals:direction=* (even in the talk page)<br>
</li>
<li><a
href="https://wiki.openstreetmap.org/wiki/Tag:highway%3Dstop">https://wiki.openstreetmap.org/wiki/Tag:highway%3Dstop</a>
encourages direction=*</li>
<li><a
href="https://wiki.openstreetmap.org/wiki/Tag:highway%3Dgive_way">https://wiki.openstreetmap.org/wiki/Tag:highway%3Dgive_way</a>
encourages direction=*<br>
</li>
</ol>
<li>Because editors use it that way... probably because they have
implemented directions following the wiki! But also because they
have implemented it for traffic lights, stops and give ways at
different point in time (and iD for instance don't support
direction for all of those features) and by different developers
(and different point of view). When you see a field in iD (for
instance), you often want to fill it when you know the answer.
When you don't see it, you may not think to create the tag by
yourself (or maybe not even know a tag exists).<br>
</li>
<li>Some quality assurance tools (such as Osmose) encourage (or
have encouraged) one form over another one, sometimes
involuntarily.<br>
</li>
<li>In real life a traffic light is more often associated to
another device such as a camera, a pedestrian light... than stop
signs which stands generally on their own. So direction=* might
be enought for stops and give_ways most of the time for most of
the mappers and editors.</li>
<li>Maybe massive edits or imports have dug the gap.<br>
</li>
</ol>
<p>I think that both stop, give way and traffic signals shall have a
consistent definition of direction and shall be consistent in
which key to encourage. As soon as direction=* is valid I would
encourage it as the primary method, would not deprecate the second
one but explain it is one way of avoiding ambiguities in some
cases.</p>
<p>Yours,<br>
</p>
<pre class="moz-signature" cols="72">LeTopographeFou</pre>
<div class="moz-cite-prefix">Le 20/03/2017 à 17:19, Jean-Marc
Liotier a écrit :<br>
</div>
<blockquote
cite="mid:20170320171913.071d293b@manantali.encara.local.ads"
type="cite">
<pre wrap="">traffic_signals:direction=* is used on 27278 highway=traffic_signals
objects:
<a class="moz-txt-link-freetext" href="https://taginfo.openstreetmap.org/tags/highway=traffic_signals#combinations">https://taginfo.openstreetmap.org/tags/highway=traffic_signals#combinations</a>
highway=stop is combined with a direction tag on about 77000 objects
(direction=backward, direction=forward and the literal direction=*)
<a class="moz-txt-link-freetext" href="https://taginfo.openstreetmap.org/tags/highway=stop#combinations">https://taginfo.openstreetmap.org/tags/highway=stop#combinations</a>
highway=give_way is combined with a direction tag on about 43000 objects
(direction=backward, direction=forward and the literal direction=*)
<a class="moz-txt-link-freetext" href="https://taginfo.openstreetmap.org/tags/highway=give_way#combinations">https://taginfo.openstreetmap.org/tags/highway=give_way#combinations</a>
Given how widely used the direction tag is for highway=* signs, why
isn't it also applied to highway=traffic_signals ? Does
traffic_signals:direction=* bear additional meaning that direction=*
does not convey ?
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</pre>
</blockquote>
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