Australian Standards also require that any trailer towed behind two wheeled vehicle be 1m wide or less.
I have heard that, but I havent been able to find that spec, and no-one has been able to say what the standard is. Its not in the Trailer standard, I have that and have read it/them, there are a couple sort of cross referenced.
I found one that says a bike is to be no wider than 1 Meter, (cant remember where but)