Quoted sections have been edited down to only show parts I am responding to:

> On Mar 22, 2017, at 5:37 AM, Greg Troxel <g...@lexort.com> wrote:
> 
> For highway=traffic_signals, the normal situation is that it's on a
> node, and affects all ways entering the node.  Or it's on a way and
> affects both directions -- in my experience, when there are traffic
> lights not at an intersection, they are always for both directions (even
> though in theory they could be set up for one direction only).

CalTrans has used semi-permanent traffic signals to control traffic flow over 
damaged road sections. A light at each side of the damaged area controls the 
sequentially one-way traffic through the damaged area that has been reduced to 
one lane operation. I’ve seen these in the Santa Cruz mountains, but the 
longest section of road I’ve seen controlled this way was on the main road to 
Yosemite Valley where the side of the mountain came down on the main roadway 
and the work around, in place for several years, was to put some pavement on 
the old single track railway grade on the other side of the river and put two 
bridges in place to get traffic across and back. It maybe still in place while 
but I’ve not been through there in several years. I know they took a long time 
to decide what to do about the still unstable mountain above the covered 
section of highway.

So there are places with traffic signals away any intersections that control 
traffic going into a one lane section. I guess a smart router could guess that 
the transition of a road from two lanes to one lane would count as an 
intersection but that seems an error prone algorithm. Having a direction tag of 
some sort available does make tagging this situation possible.

> As a human, if I see a highway=stop on a way about 3-10m from an
> intersection, it's obvious that it applies to travel on the way towards
> the intersection, but not leaving the intersection.  However, I think
> OsmAnd sometimes falses on these.

OsmAnd always seems to “false on” these. To the point where I ignore the stop 
warning it gives.

> I would suggest a definition that associates the stop sign with the
> nearest intersection if it's less than 25m away, and there are no
> intersections in the other direction within 3x that closest intersection
> distance.  And then to use relations to label which intersection, if the
> above doesn't work.

Sounds like a reasonable thing to add some distances to the wiki where it 
describes that algorithm but without specific distance numbers.

> . . .   I view this whole exercise as designing tagging rules
> that are good for human editors and acceptable (semantically non-kludgy
> and reasonably easily implementable) for data consumers.

+1 on that.


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