They are not as common in Germany as in France in my experience. I would rather prefer to visit a german castle than waiting for the Stau to disappear.
In Germany, there's a guideline for a minimum distance between such signs so that they still stand out. Though I have seen a few that were closer than the supposed minimum of 20 or 30 km or so.
In Germany, there's a guideline for a minimum distance between such signs so that they still stand out. Though I have seen a few that were closer than the supposed minimum of 20 or 30 km or so.