[Tagging] traffic_signals:direction=* vs. direction=*

[Jean-Marc Liotier]

So, summing up the ideas expressed so far, in the example case of a stop
sign on a two-ways way (not an all-ways stop), we have:

1- highway=stop+direction=forward node on the way to an intersection
- Advantages: simple, uses the well-known direction=* tag, easy for
  routers to interpret
- Disadvantages: to be unambiguous, must be tagged on a
  non-intersection node adjacent to the intersection to which it
  applies, only good for covering the simple case, which
  means that it requires another way to coexist for covering the
  complex case
- My opinion: looks good to me for covering the simple case, which
  means that it requires another way to coexist for covering the
  complex case. Is the simple case common enough for this duplication
  to be a net benefit ?

2- highway=stop+stop:direction=forward node on the way to an
  intersection
- Advantages: simple, uses the stop:direction=* tag which is coherent
  with traffic_signals:direction=*
- Disadvantages: new tag, to be unambiguous, must be tagged on a
  non-intersection node adjacent to the intersection to which it applies
- My opinion: just like n°1 but with an exotic tag for no benefit...
  Discard this proposal !

2- highway=stop node on the way to an intersection, with the nearest
  intersection being the one to which the sign applies
- Advantages: simplest method
- Disadvantages: slight processing burden for the router which must find
  the closest intersection to guess which one it applies to
- My opinion: might be too ambiguous for the routing processor, but I'm
  not operating a routing system so maybe someone who is might offer
  his opinion on that point

3- highway=stop on the right of the way when looking towards the
  intersection to which the sign applies
- Advantages: very simple, records actual location of the stop sign
- Disadvantages: heavy processing burden for the router which must find
  the closest way to guess which one it applies to
- My opinion: way too much burden on the routing processor... But
  again, I'm not operating a routing system so maybe someone who is
  might offer his opinion on that point

4- highway=stop near the way, with a two-node way attached as a
  "direction arrow"
- Advantages: well, it sort of would work
- Disadvantages: way too much burden on the routing processor, heretical
  to the Openstreetmap way
- My opinion: heretical !

5- relation (type: to be defined) including highway=stop and
from:forward (the incoming way arriving at the stop - must be connected
to the stop)
- Advantages: only a couple more additional tagging steps compared to
  the other methods (creating the relation+a couple members).
  Compatible with the highway=stop being either on the way or near the
  way at the actual location of the sign
- Disadvantages: a couple more additional tagging steps compared to
  the other methods... And it is a relation (which is not
  beginner-friendly)
- My opinion: must be retained because it is the only one which
  unambiguously covers all cases. The only question is: is it valuable
  to have another simpler relationless method to cover the common
  simple case ?

My opinion summary: n°5 is a keeper... Do we need n°1 too ?