I've put up here some pictures of Australian roundabouts. I checked more than
one source for information on mini_roundabout and found no consensus. German
precision was noted on wikipedia, but the writer had left some potential
sizes out of the list, and the UK style of paint on the road in a whimsical
circle was not found elsewhere in the world.
These small ones I've photographed are within Brent's definitions, where a
mini_roundabout fits within the width of the road.