[OSM-talk] Bridges / viaducts for railways

[Michael Collinson]

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.

Mike
Stockholm

*  And before I set off storms of UK protest again, I mean remove it 
from map features NOT preventing anyone using or rendering it! :-)