Mythbusters compared a four-way intersection vs a roundabout to see how many cars could pass through in two 15 minute tests. The results? Four-way intersection: 385 vehicles, roundabout: 460 vehicles. The roundabout improved traffic flow by ~20 percent.
Carmel, Indiana has more roundabouts than any city in the US. “Roundabouts have replaced signals or stop signs at intersections, the number of injury accidents has been reduced by about 80 percent and the number of accidents overall by about 40 percent.”
Source: Carmel Indiana
“Drivers use about 30 percent less gas when using a roundabout compared with a traffic signal, according to the Institute, because they don’t necessarily have to stop and idle.”