[Tagging] Tunnels and bridges

Peter Wendorff wendorff at uni-paderborn.de
Thu Jan 31 14:02:18 GMT 2013

Am 31.01.2013 14:44, schrieb Martin Vonwald:
> In my opinion this is a rather obvious approach therefore I'm not
> surprised that someone already came up with it earlier. But I am
> definitively surprised that we don't have any documentation in the
> wiki for it. I see a lot of bridges with many ways running over it
> (two footways, two cycleways, two carriageways) and on the map it just
> looks AWFUL! But the renderer can not display it any better because it
> doesn't have the appropriate information.
> So I would suggest that we decide which tag would be good for the
> bridge, document it and start tagging it this way to get things going
> ;-)
> Let's first concentrate on bridges. In my opinion we need the following tags:
> * bridge=<type> : use this tag just like it is used at the moment. If
> the value would be "yes" it should be optional.
+1 for using bridge=type, -1 for defining it as optional.
> * layer=<x> : this should get the same layer as the ways running over
> it. One could argue that this should get a layer below the ways, but I
> find this rather counter-intuitive. See comment below!
+1 for setting it the same layer as the ways running over it.
Using even more layers would increase the confusion when using more than 
one layer (two if you count the "default" one), as it would double the 
layers. Especially it would require changes to existing layers when 
"extending" existing bridges with the bridge-building-area proposed here.

One remark where you don't provide a solution, but where I don't have 
any solution either is the other way around:
You/we propose here a way to define "these ways share one bridge 
structure", but it's plugged in to the existing osm database, so there 
are already many bridges where the bridge area would fit, but is missing 
(as it wasn't defined/proposed up to now).
If we would propose a solution to state "this is  single-way-bridge as 
it is mapped here currently", QA tools could check both variants for 
completeness instead of asking ever and ever again something like "these 
n bridges run approximately in parallel near to each other. If the ways 
share the same structure, please add a [bridge-area] for the area 
covered by the bridge structure."
To solve that probably an additional tag for "single" bridges would be 
useful: standalone_bridge=yes (I don't like the wording here, but you 
get the point).

As a second remark I would like to ask how to define the bridges pillars 
(in the middle or at both ends of the structure).
Being able to map them would allow
1) better 3D rendering
2) interpreting them as barriers under the bridge
3) more or less calculate an estimated space width for driving through 
under the bridge


2013/1/31 Pieren <pieren3 at gmail.com>:
>> On Thu, Jan 31, 2013 at 2:06 PM, Martin Koppenhoefer
>> <dieterdreist at gmail.com> wrote:
>>> I wouldn't call this a "bridge", it is a vault, but the "bridge" (or
>>> viaduct) if you wanted to map it would (IMHO) be the structure as a
>>> whole, not just a single segment.
>> Instead of "building=bridge", you might choose "man_made=bridge_deck"
>> or simply "bridge=deck" ?
>> Btw, the idea is not new. Check this bridge I traced in march 2010:
>> http://www.openstreetmap.org/browse/way/53582123/history
>> I used the tags combination "highway=bridge" + "area=yes". Then it was
>> replaced by "bridge=yes" + "area=yes" and finally by
>> "building=bridge".
>> I guess the "building=*" tag is used for rendering purpose. Which is
>> not correct.
>> Pieren
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