They use similar signs on the highways here in Stuttgart. I have a mixed view of them, sometimes the speed changes seem arbitrary.
There is a spot on my morning commute where they constantly drop the speed from 100 km/h (62 mph) down to 80 Km/h (49 mph). All it seems to do is cause backups, the traffic thins as we pass a major interchange with the A8 autobahn.
THe signs are only as good as the evaluations of traffic.
Stuttgart, my oh my. I was stationed in Goppingen, back in 1966-67. My buddy’s, 1953 VW, just could make 80 Km/h. Loved being stationed over there.