Advertising control exists so that advertisements and associated structures complement (or at least do not unreasonably detract from) desirable characteristics of the natural and built environment in which the advertisements appear.
Local laws permit certain advertising signs, and you may erect these without seeking approval. Contact council to determine whether the sign you wish to erect requires approval.
If you are advertising on a state controlled road, contact the Department of Transport and Main Roads for information on the State Government roadside advertising policy.