As has been mentioned already, they are plentiful in Massachusetts and the word "rotary" is a household word. If you were to say "roundabout" here in MA, hardly anyone would have any idea of what that is. Some would ask if you are talking about the 70's song by the band Yes (pretty good number).
Also, the rule is that a driver entering a rotary must yield to any vehicle already in the rotary. Once you know that, you should be able to navigate them.
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