FYI:
http://www.lawhandbook.org.au/handbook/ch10s02s03.php#
POLICE
Police are allowed onto your land if they have a warrant, which they should show you when seeking entry to your land. If they don't have a warrant, they may only enter your land if you invite them, or if particular circumstances arise, such as making an arrest, stopping a breach of the peace or ensuring that the SOA is being complied with (see: "Power to search without warrant", in Chapter 3*2 Arrest and Interrogation).
POWER TO SEARCH WITHOUT WARRANT
Victorian offences
Section 459A of the Crimes Act (Vic) gives a member of the police force power to enter and search any place without warrant for the purpose of arrest where it is believed, on reasonable grounds, that a person may be found, who:
has committed a serious indictable offence in Victoria; has committed an offence elsewhere which, if committed in Victoria, would be a serious indictable offence; has escaped from legal custody; or is committing a serious indictable offence.
A serious indictable offence in this context means any offence for which the law provides for imprisonment for life or for five years or more (s.325). This includes offences such as theft (including shoplifting) as well as the most serious offences, such as armed robbery, rape or murder.
Still trying to find if your driveway is public/private though....