[OSM-talk] Bridges / viaducts for railways

[Dave Stubbs]

On Jan 29, 2008 8:13 AM, Michael Collinson <mike at ayeltd.biz> wrote:

> At 06:57 PM 1/28/2008, Tom Chance wrote:
> >Hello,
> >
> >I'm a bit confused about these tags:
> >
> >railway=viaduct
> >bridge=yes
> >cutting=yes
> >embankment=yes
> >
> >I assume that 'viaduct' covers these sort of elevated rail lines so that
> >bridges are just for, well, bridges over other ways:
> >
> http://www.mybrightonandhove.org.uk/images/uploaded/scaled/railway_viaduct_aerial.jpg
> >
> http://www.betterpublicbuildings.gov.uk/assets/images/finalists_2006/jamestown/jamestown_large.jpg
> >http://www.24hourmuseum.org.uk/content/images/2005_1745.JPG
> >
> >Why is it not a property like bridge, cutting etc. and will it render
> >correctly? Should it be changed to viaduct=yes?
>
> This is one of those "old" tags.  Both bridges and viaducts were
> originally nodes.  I also think it reflects the earlier more
> UK-centric tagging - "viaducts" are to the non-specialist those 19th
> century long tall multi-arched stone bridges that grace many an
> English valley and town. I ignore it entirely.  Certainly if used,
> viaduct=yes would make more sense.
>
> As to way forward, I suggest there are 3 options:
>
> - Depreciate the viaduct tag entirely [*]
>
> - Use viaduct=yes
>
> - Complement the generic bridge=yes tag and develop a specialist
> bridge type tag for bridge devotees with precise
> architectural/engineering definition.
>


>From what I think I understand, the railway lines out of Waterloo station in
London are pretty much going to be classed as going over a viaduct all the
way to Clapham Junction? These are raised manmade structures about the
height of a house, mostly with arches etc. Same for lines coming out of
London Bridge and most other London stations. In fact the district line
(railway=>subway) between Parsons Green and East Putney is also viaduct?

On that basis calling them a big long bridge doesn't really make much sense
(we're talking at least several km/miles here), so we're probably best off
with viaduct=>yes. Currently they're mostly just set at level=>1 without any
specialist tagging for what they're going over, not even bridges over the
roads.

Dave
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