[Tagging] Chaos and uncertainty in "bridge"

Volker Schmidt voschix at gmail.com
Mon Jan 16 18:49:42 GMT 2012

> 1. There is a first classification system using the kind of way going
> over it for distinction:

which is inherent in the way or other structure that is tagged with
"bridge": highway, railway, waterway, pipeline

> 1.1 A road (or railway): "viaduct" (a term that is not really well
> defined, especially the distinction between a "bridge" and a "viaduct"
> doesn't seem to be clear). This is a bit mixed because besides the
> road this seems to be a bridge with several abutments in "small"
> distances, whatever "small" is, and "viaduct" seems to be used also in
> conjunction with railroads. Not sure but I feel as "viaduct" might
> also be a bridge typology (see 3).

For me the viaduct is a specific type of bridge, i.e. one that has
intermediate pillars in addition to the end supports

> 1.2 Water: "aqueduct" (suitable for the parts of aqueducts that span
> over a void). The definition seems to extend the use to all kind of
> aqueducts ("A longer structure for carrying a canal or fresh water.")
> while many aqueducts are not spanning over something (they are tubes,
> have a solid support like a wall without openings or even are
> underground) so they clearly aren't bridges.

If it is open water like a canal bridge, this is waterway=canal and
bridge=viaduct (for example). If the water flows in a closed structure:
man_,made=pipeline type=water bridge=yes

This first system doesn't make much sense IMHO, because you can
> already see by other tags which kind of way is on top (waterway,
> highway, railway), but it is currently the most used.
> 2. Another classification system on the page is one according to the
> structural system employed:
> 2.1 arch
> 2.2 pontoon
> 2.3 suspension
> 3. And even another system is that of typology:
> 3.1 bascule
> 3.2 drawbridge
> 3.3 humpback
> 3.4 lift
> 3.5 swing

I don't see anything wrong with todays tagging.
Bridge is an additional key to the main way (highway, waterway, railway,
other man_made structure) that initally can laso be ommitted.

The key bridge can have a value that decribes the type of bridge, i.e.
yes (generic)
Note that the non-generic bridge types are all mutually exclusive, I do not
see the difference between typology and structural system.

"so why is this bad?" one might argue. Well, the problem is that with
> this chaos you won't be able to tag all properties (typology,
> structural system, carried way) of a bridge, you will instead have to
> decide which one to focus on (might also lead to tagging wars).
> Another problem is that the lack of systematics makes it difficult to
> extent this system with new values, because it is not clear where the
> focus is.
> I propose to use distinct tags for these properties instead:
> 1. is not needed IMHO (see above). If the interesting fact for
> viaducts are the several "small" spans I'd put this into typology.
> 2. could be tagged with bridge:structure (or structure or
> structural_system)
> 3. could be tagged with bridge:type (or type).

I do not see the need to change the tagging system

Last but not least I'd like to ask you for comments on 3 new values:
> N1. a bridge made of few ropes where you walk on a rope:
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Kaiserschild_1.jpg
> http://www.gruppenstunden-freizeit-programme.de/ferienlager-freizeiten-erlebnisse/freizeit-bilder/seilbruecke/Piratenlager-05-262.JPG
> http://www.bergsteigen.at/pic/d6025434-21f9-4d93-9ce9-42aba5cf00db.jpg
> additionally we could tag the amount of ropes (or even more precisely
> the amount of "upper" and "lower" ropes)
> are these described in English with the term "zip-line"?
> http://en.wikipedia.org/wiki/Zip-line
> N2. a similar bridge made of ropes, but you walk on planks:
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Trift_Bruecke_1.jpg
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Tripsdrill.jpg
> I guess this would be a "simple_suspension_bridge"
> N3. A "Cable-stayed_bridge" (the absence of this value makes it
> probable that most of these might currently be tagged as suspension
> bridges or not classified at all). The difference from a suspension
> bridge is that the cables are directly attached to the towers / pylons
> instead of to another cable, see here:
> http://en.wikipedia.org/wiki/Cable_stayed_bridge

I have got the impression that we are overdoing things here.

For me these are all some variants of foot suspension bridges. See
http://en.wikipedia.org/wiki/Suspension_bridge and

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