I'd think German traffic engineers could come up with a better solution, yet these are everywhere:
The bike paths themselves are desire paths for cars and motorcycles.
To block them off, they put up barriers, but those also block cargo bikes, wheelchairs and strollers, create a collision hazard, and force all cyclists to stop and dismount for no reason.
Of course, they'll be bypassed wherever possible โ naturally by cars and motorcycles too, if there's enough room.
Hinges: some do, but they are typically locked with a key. The easiest would be bollards ("poller")
Blue sign means: pedestrians and bikes have to use this, and they share the path. If the line would be vertical, it would mean bikes/pedestrians have their own lanes