See http://wiki.openstreetmap.org/wiki/Map_Features#Railway

Railway types: rail, tram, light_rail, abandoned, disused, subway, preserved, narrow_guage, construction, monorail, funicular. Sidings supported in the service tag.

Note that bridges can be derived from bridge_cl. Needs to be cut and merged?
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RP: name needs to be added in a relation, so both ways (if there are 2) can be grouped together and named
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