[Tagging] Dispute prevention: meaning of lanes tag

[Martin Vonwald]

Hi!

I'm planning to improve the articles (english, german and russian) for
the lanes-tag (http://wiki.openstreetmap.org/wiki/Key:lanes). Right
now a few points are left open and desperately need some
clarification. As some of the latest changes lead to some dispute (see
[1]) I will let you know what I would like to add/update.

* The lanes tag should count all lanes which are wide enough for
motorized vehicles other than motor cycles  (see [2]). This is (more
or less) the way as it is written in the english and russian article,
but not e.g. in the german. I will add also a link to the UN Vienna
Convention and try to think of an easier understandable wording
compared to the official text.
* PSV lanes SHOULD be included (also [2]). Example: lanes=3 and
lanes:psv=1 means we have three lanes and one OF THEM is for PSV only.
* Cycle lanes should NOT be included (see [3]), because they are not
"wide enough for one moving line of motor vehicles other than motor
cycles".
* Parking lanes/spaces should NOT be included (see [4]).
* Turn lanes SHOULD be included (see [2] and [5]).
* The lane count should change, as soon as a) new lane has reached its
full width or b) a lane starts to disappear (usually a merge with
another lane) (also [5]).
* Partly taken from the current german page I would add the following
assumptions for roads without explicit lane count:
  - A one-way road has one lane
  - Two-way roads have two lanes, one in each direction
  - Two-way roads with a specified lane count, but without a specified
lanes:forward OR lanes:backward and a lane count, that is divisible by
two, are assumed to have half of the lanes in each direction, e.g.
lanes=4 means two lanes in each direction if not specified otherwise.
I will add a recommendation for this situation, to add explicit
values.

I'm not sure what I should do with the comments about sidewalks. They
don't have anything to do with lanes (neither motorized traffic, psv,
cycle lanes, whatever), so they actually don't belong here. Maybe just
a link in Related Tags?

Martin

[1] http://lists.openstreetmap.org/pipermail/tagging/2011-September/008532.html
[2] http://lists.openstreetmap.org/pipermail/tagging/2011-September/008578.html
[3] http://lists.openstreetmap.org/pipermail/tagging/2011-September/008582.html
[4] http://lists.openstreetmap.org/pipermail/tagging/2011-September/008587.html
[5] http://lists.openstreetmap.org/pipermail/tagging/2011-September/008596.html