South Australian Numbered Regulations South Australian Numbered Regulations145—General coupling requirements
(1) A fifth wheel coupling, the mating parts of a coupling, a kingpin or a towbar must not be used for a load more than the manufacturer’s load rating.
(2) A kingpin must be used only with a fifth wheel coupling that has a corresponding jaw size.
Example—
An adaptor must not to be used to fit a kingpin to a fifth wheel coupling.
(3) The mating parts of a coupling used to connect a semi-trailer to a towing vehicle must not allow the semi-trailer to roll to an extent that makes the towing vehicle unstable.