How to tag them?
Should I make multiple parallel roads or create some kind of “bridge area”?
Depends on the bridge 
Example A: Road with boardwalk, boardwalk free for bicycle and pedestrians. Just add bridge=yes and layer=+x with foot=yes and bicyle=yes.*
Example B: Railroad bridge with seperat footway: 2 parallel ways (1 railroad=rail, 1 highway=footway) both with bridge=yes and layer=+x (footway with bicyle=yes if allowed). You can now combine these 2 ways in a relation: http://wiki.openstreetmap.org/wiki/Relations/Proposed/Bridges_and_Tunnels
- If the bridge has a name different from the name of the street you should also use a relation here.
Thanks. This would be a railway bridge with two boardwalks on either side. They are not separated anyhow, so I guess it’s case A, with joining the path to the railway. I doubt it would be properly rendered, though.
More questions about parallel roads:
How to map a cobblestone road with tracks (grade 2, one way) on both sides? The “main” part of the road is the cobblestone, but most cars use tracks instead.
What to do if such a track is only on one side?
That sounds strange to me. A footpath besides a railroad-track without any seperation… Is this legal walking on / beside the railroad-path? Anyway. With highway=* I assume that there is some kind of boardwalk or footway following the lane for cars (except highway=motorway aso.). With a bridge tagged as railway=rail I wouldn’t think that I can use this as a pedestrian. Perhaps it’s something with local conventions? Here in Germany many railroad bridges can be used by cylists and pedestrians, but the have their own path on the bridge.
Oeh… Can’t quite imagine what you’re talking about. 3 parallel ways (track, cobblestone, track) and all 3 are used by cars? Do you have a link with a photo you can post here?
I’m not sure about that. There is a “terrace” with barriers where people can stop to look at the view, the paths going to the bridge are used by both cyclists and pedestrians, but I witnessed a situation when train stopped waiting for some people to get off the bridge (the driver wasn’t happy about this), even though the footways are away enough for the train to pass.
Most of the railroad bridges I saw have some kind of a footway by the tracks, but I wouldn’t risk calling it a convention.
I guess I will just wait for the bridge relation to become more than proposition and make the path overlap with the bridge part of the railway.
You got it right. The 3-ways road was recently repaved, so I can’t provide a photo. I will try to make a photo of the 2-ways road today.
Railroad-Bridge: I’d suggest to map this as seperate ways (footpath,rail) both as bridge=yes and layer=1. If necessary combine these as a bridge relation. I guess the footpath is for railroad-personnel only (maintainance aso.) and forbidden to normal pedastrians. So to prevent rounting software to navigat pedetrians over such bridges I recommend to tag the footpath as access=private.
3 parallel ways: Map what you see. If there are 3 different ways than map it as 3 parallel ways.
Interesting question to all other readers: How can we indicate that these 3 ways are in fact 3 lanes of the same road and you can switch everytime from on way to the other?