This road sign

Erklärung
The red-bordered circular 40 sign sets the maximum lawful speed at 40 km/h. A recommended speed would appear on a blue square, while a blue circle would impose a minimum rather than cap the speed.

The red-bordered circular 40 sign sets the maximum lawful speed at 40 km/h. A recommended speed would appear on a blue square, while a blue circle would impose a minimum rather than cap the speed.