A rotary is an interesting circular traffic formation that not many people will ever run into. From what I hear it is native to the greater New England / eastern seaboard area (I think extending down into New Jersey), which is infamous for their overuse. Rotaries are also known as Traffic Circles (as my New Hampshire geek girl informs me).

Rotaries are a circle of road from which many exits are possible at different locations of the clock. Traffic flows in these rotaries counter-clockwise, until the people reach their designated exit. There are usually two lanes to a rotary: the inner "drive around" lane, and the outer "I'm going to get off soon" lane. You can maximize the choices in a road by creating several different outlets to one rotary.

By law, these rotaries are always well marked, and you need to yield to traffic that is already in the rotary. This setup, by nature, is a situation where only the aggressive survive. If you are not aggressive enough to change lanes at the right time, or get in at a high speed, then you will either be stuck waiting, or stuck in the middle ring of the rotary. New England Drivers usually are fairly adept at these "go for it"-type intersections, but the rotary holds a special place in many people's hearts, especially the non-native drivers, who have trouble wrapping their brains around this odd traffic control device.