In Queensland a roadworthy certificate is called a safety certificate.
A safety certificate is needed when a registered light vehicle is offered for sale in Queensland, or when re-registering an unregistered vehicle. It confirms that a vehicle has passed a minimum safety standard inspection.
Vehicles requiring a safety certificate are:
trailers (including caravans) with an aggregate trailer mass (ATM) of 750kg-3,500kg
any other vehicles up to 4,500kg gross vehicle mass (GVM).
This inspection covers the basics for the safe operation of the vehicle, such as:
body rust or damage
A safety certificate inspection is not a comprehensive mechanical inspection. If you are buying a used vehicle, you should contact a motoring group such as RACQ for a full mechanical inspection.