Drivers are puzzled by mysterious traffic signs at traffic lights. The signs are not relevant for private drivers, but for drivers of public transport vehicles.
The forest of signs in Germany seems to be unfathomable. For example, only in Heidelberg is there a flashing “WF” for turning. In Stuttgart, there is an “A’ (requirement) instead of the “K” in Berlin. In Ulm, a glowing triangle means “continue driving but give way”