What does this combination of tags mean? Is it worth documenting? (It’s not mentioned on the Wiki) Has it been used to “translate” a specific traffic sign into OSM tagging, maybe something like pedestrian and cycle zone? When you map a highway=pedestrian, how do you decide between bicycle=yes and bicycle=designated?
More generally, when do you put bicycle=designated on a street? (unclassified, residential, …)
The Versatiles Colorful style renders streets with bicycle=designated differently so that makes them easy to spot (example here). In an area I am looking at, I can’t make sense of which pedestrian streets have bicycle=designated and which ones have yes. Some pedestrian streets don’t have a bicycle tag at all, and I’ve noticed that OSM-based routers make different default assumptions for biycle access on pedestrian, so adding explicit tags is probably a useful activity.
I checked the only occurrence in my area and it was a tagging mistake. Someone tagged designated instead of dismount. I don’t know if any sign explaining this tagging in German speaking countries.
I would argue that foot=designated is implied by highway=pedestrian, no need to tag it explicitly. With this sign, bicycles are allowed, so bicycle=yes. The way/area is not “the way to go” for cyclists, so it’s not bicycle=designated.
I can imagine situations where cyclists are supposed to use a pedestrian way or area. Particularly when cycling (trekking bike) in German and Italian cities I was often forced off the road onto the sidewalk or to a separate pedestrian way/area, not part of this road. Only last year’s trip in Italy we noticed that the signage for cyclists in these situations is improving, but not yet sufficient. By far.
I think this will naturally differ by country. In the U.S., we’ve taken designated to mean more or less “designed for” or “intended for” in many contexts. It’s a more holistic standard than in some other countries. If we had to strictly map bicycle=* to standard MUTCD signs, we would do something like what’s documented on the wiki:
no
yes
designated
However, this only works in theory. is relatively rare and only posted on dedicated trails or sidepaths, never in a situation where bikes share the road with traffic or where a pedestrian mall has plenty of room for all non-motorized traffic. isn’t just an access sign; it can also indicate lcn=yes, or that the street is a bike boulevard. In practice, permission for non-motorized vehicles isn’t consistently signposted, and few off-road signs adhere to any standard to begin with.
I would expect road sized structure, marked as combined footway and cycleway (either with segregation if segregated=yes or with no segregation between traffic modes if segregated=yes)
If bicycle traffic is merely allowed or exempt from ban on vehicle traffic then it bicycle=yes
Never, though if road has say sharrows/bicycle lanes then I would not remove it.
is relatively rare and only posted on dedicated trails or sidepaths, never in a situation where bikes share the road with traffic or where a pedestrian mall has plenty of room for all non-motorized traffic. 
isn’t just an access sign; it can also indicate 