Australian Dangerous Goods Code Edition 7.8 (Consignor and Transport Duties) 5.3.9: Remove placards only when freed of dangerous goods, and always once freed

What does 5.3.9 require?

Once a placardable unit, portable tank, bulk container, road tank vehicle or rail tank wagon has held dangerous goods, its placards stay on until every receptacle, tank and compartment has been emptied and freed of the goods; as soon as a unit or cargo transport unit has been freed, the placards come off, and a placard for a particular hazard comes off once that hazard is gone. Contaminated cargo transport units are subject to the limits in 7.1.7.1.2.