Roundabouts aren't great for high-volume locations. This new design, called the "Vortex Junction," handles a plethora of intersections and many, many plethora of cars in a simple, ingenious layout. The future of grandma-and-Griswold-confusing intersections, below.
Roundabouts work great in low traffic volume areas because the number of vehicles in the intersection at one time is low. They eliminate traffic stops like signs or lights and allow traffic to move smoothly. When they're installed in high traffic areas, roundabouts can become a nightmare. The trouble with roundabouts, especially big ones, is drivers are always jockeying for position along the outside lane since there are always vehicles entering into, in the intersection and attempting to exit along the outer diameter. This is a problem the Vortex Junction solves.
In the Vortex, traffic entering the intersection uses the outside lane, then transitions to the inside exit lane, which then transition to an off ramp and either goes over or under the circular lane. It eliminates the trouble of entering motorists fighting exiting motorists for position, and vice versa. It has several benefits, first, it can efficiently handle many incoming roadways from any approach angle, it cuts down on the number and size of stacked spaghetti-type intersection bridges while keeping most of the infrastructure on the ground, plus, relative to the big monstrosities in some freeway intersections, it's relatively cheap. Another happy benefit is a use-able center section which could be prime places for things like sports stadiums or convention centers which generate spikes in traffic. As far as we know, there are no plans to build any of these intersections at this point, but the designs Japanese creators are shopping it around to cities and countries trying to license the Vortex. We'd be interested to test over- and understeer on those decreasing radii. [Yet2]