There's no reference to a vehicle needing to be roadworthy in the Vic road rules.
http://www.austlii.edu.au/au/legis/v...09289/s15.html
I'm aware of the obvious danger of unroadworthiness, but where do you draw a line? I believe anyone with two or more brake lights out should be taken off the road (and I see at least 5 per day), but it's maybe not as dangerous as bald tyres.