[Tagging] Proposed feature: Railway Signals

[Michael Zangl]

Hello,

I have written a proposal that allows you to map signals. The signal
itself is mapped as railway=signal the way it is done already and
proposed in the railway proposal.

What I add is a method to add more tags to a signal.

The tags are meant for people who want to do railway simulations or
special railway maps based on that data, other people are normally only
interested in: is there a signal or not (as much as they are interested
in: is there a tree).

What I also proposed is that signals are placed aside the track, with a
relation that points to the track they belong to and for some signal
types (crossing, advance signals, ...) the thing they protect.

There was a lot of discussion about directions and relations, so I don't
want to trigger an other general pro/con-relation discussion here. I
think that at this point, relations should realy be used for some
signals that are in a special relation to other things on the tracks.

What I hav not added yet (also because of that discussion) is the
forward/backward-definition, which is (for the railways operation) realy
important, but I do not know the best practice for the new proposal. One
could add it as tag to the signal node itself (would save relations for
reverse signals, but there are many problems: What to do if there are
two/three/more ways going on from that point (e.g. a junction with a
junction signal beside it, as it normally is...). Tagging a junction
with a relation is simple: Place the sign on the side it is on, add it
to the relation, the junction node as "for" and the track of the
junction as "track"-role) or we could add the tag to the relation (as
role of the track) which would place the data at the right point.

For most signals, no relation is needed because they are only on a main
track. Signal mapping only makes sense if each single track is mapped,
because they differ most of the time for two-track lines.

Maby we can also decide on only one possible mapping method, where I
would prefer relations.

Link to the proposal:
http://wiki.openstreetmap.org/wiki/Proposed_features/Railway_Signals
Please discuss stuff, that is only related to the proposal, there.

Michael