What characterizes roundabouts?

Roundabouts are circular intersections designed to facilitate continuous traffic flow around a central island. Vehicles approaching a roundabout yield to those already circulating, which minimizes the need for stop-and-go traffic and reduces the likelihood of severe collisions. This design promotes a smoother transition through the intersection, allowing for a more efficient movement of vehicles.

While some intersections may require complete stops, this is not a characteristic of roundabouts, where the emphasis is on maintaining a flow. Similarly, roundabouts do not typically involve traffic lights, which are common in signal-controlled intersections, and they are explicitly built for vehicular traffic rather than being exclusively for bicycles. Hence, the defining feature of a roundabout is its circular shape with one-way traffic flow around a central island, making option B the most accurate description.