When must a school bus be marked with orange school bus signs?

In Germany, a school bus must display orange school bus signs specifically when it is transporting school children. This is to alert other road users to the presence of children who may be entering or exiting the bus, increasing the need for caution. The signs are not required before or after transporting children, only during the actual transport. This rule helps enhance safety for the children by making the bus more visible and signaling drivers to be particularly careful.