Apart from the people who don't know how to use traffic circles (and there aren't enough expletives in the dictionary to properly describe how I feel about them), two other groups of idiots piss me off.
People who don't care how a traffic circle is supposed to work, and follow the 'right of way' principle: I'm right and you're in my way. Look outside The Glen in Jo'burg Souf, any day of the week. (Too many 'roid users in the Souf, I guess).
And traffic engineers (well, all engineers actually), who design two lane circles smaller than 100m diameter. If the distance between the first exit and the third is 70m, how the **** do they expect cars to enter AND exit the inner lane in that time, without coming to a compete stop (because of people entering the outer lane at the second exit), or driving like they own the road? Engineers are lower than pond scum, but traffic engineers make mechanical engineers seem like saints.