We were asked to test and improve the working of a 2 mile long urban expressway with 3 crossroads one after the other.

Here thanks to our simulation, we discovered an original traffic detail : with constant flow and geometry, the working of a roundabout depends largely on the conditions determining the arrival of traffic.

With random traffic (an isolated roundabout, with no crossroads, no any roundabout nearby), the roundabout is congested along one of its feeder road.		With controlled traffic, (positionning of traffic lights before the roundabout) For the same geometry and the same amount of trafic flow, the roundabout becomes fluid.