[Tagging] How to tag: Legally separated ways

Simone Saviolo simone.saviolo at gmail.com
Tue Oct 16 08:23:06 GMT 2012

2012/10/15 Johan C <osmned at gmail.com>

> I think there's some confusion here. Imagic's question was on a motorway
> example.

Where did you get this from? Sure, he referred to a picture with the model
of a motorway, but he esplicitly said "consider only section 5". We're not
talking about that section 5 *on a motorway*.

Also, your distinction motorway / non-motorway is meaningless. Motorways
are usually mapped with two separate ways because they, uh, are physically
separated carriageways. There's a guard-rail, or a new jersey barrier,
sometimes even a ditch or a gap between bridges. There used to be (at least
in Italy) motorways with a single carriageway, where lanes were separated
by a painted line; this was not a physical separation and would be tagged
as a single way.

> 2. An OSM'er started a discussion on a German page:
> http://wiki.openstreetmap.org/wiki/DE_talk:Tag:highway%3Dmotorway_link.
> It seems that the current wiki on motorway_junctions requires the start of
> the split to be at the beginning of the deceleration lane.  "In der Regel
> ist das der Punkt, an dem die Ausfädelspur beginnt oder die Auffahrt von
> der kreuzenden Straße abzweigt." Thus, the current osm tagging standards
> imply that Imagic's option a is wrong (option b too by the way [?]).

As I said above, for short sections of legal separation (white paint)
immediately followed by a physical separation (the guard-rail) I am in
favour of anticipating the split, just like it has been suggested in the
discussion you talk about. What I'm modeling this way is that there is in
fact a physical separation, and I'm just being imprecise about where the
separation starts. I advocate this imprecision because it has advantages on
the topology of the split (Y-shaped rather than T-shaped), and an early
indication is better than a late one.

> 3. You could have guessed, but i'm in favour of the way OSM is being used
> at this moment, so option b. My arguments are about the same as Colin's.
> And because I like the current tagging as shown in above examples.

You may be confused about this. The "current tagging" is in fact option A:
where the carriageways are physically separated (or at least a single
continuous strip of asphalt is divided by a physical barrier), draw two
ways; otherwise, a single one. Your motorway examples are examples of
option A. The fact the we split ways entering a large roundabout is my
bending of option A: the way is split where the white paint begins (instead
of where the kerb with grass begins) for better topology. I fail to see
where a Main Street with no barrier in the middle is drawn as two ways
(don't bring me a couple of examples, name a country or a community that
does this).


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