However, on checking the model "Australian Road Rules" 2012 I am not so sure.
Essentially the rules state that cyclists can ride abreast on roads including "bicycle path, shared path and any shoulder of the road". (Yes, I appreciate that states can vary from time to time but I would not imagine that all states have chosen to ignore this one rule.)
So, are cyclists indeed allowed to ride two abreast on cycle paths etc?
(If responding, it will be useful to quote what state you are talking of.)
http://www.ntc.gov.au/filemedia/Reports/ARRFeb12.pdf pp 136-137
151 Riding a motor bike or bicycle alongside more than 1 other rider
(1) The rider of a motor bike or bicycle must not ride on a road that is not a multi-lane road alongside more than 1 other rider, unless subrule (3) applies to the rider.
Offence provision.
Note Bicycle, motor bike and multi-lane road are defined in the dictionary, and rider is defined in rule 17.
(2) The rider of a motor bike or bicycle must not ride in a marked lane alongside more than 1 other rider in the marked lane, unless subrule (3) applies to the rider.
Offence provision.
Note Marked lane is defined in the dictionary.
(3) The rider of a motor bike or bicycle may ride alongside more than 1 other rider if the rider is:
(a) overtaking the other riders; or
(b) permitted to do so under another law of this jurisdiction.
Note Overtake is defined in the dictionary.
(4) If the rider of a motor bike or bicycle is riding on a road that is not a multi-lane road alongside another rider, or in a marked lane alongside another rider in the marked lane, the rider must ride not over 1.5 metres from the other rider.
Offence provision.
(5) In this rule:
road does not include a road-related area, but includes a bicycle path, shared path and any shoulder of the road.
Note Bicycle path is defined in rule 239, road-related area is defined in rule 13, shared path is defined in rule 242, and shoulder is defined in
rule 12.