A roundabout directs and organizes traffic, it keeps traffic moving; here, it’s the traffic that moves the roundabout, that keeps the roundabout going. The roundabout is ‘made’ by traffic; the roundabout changes its shape as cars drive by.

When the roads are empty, the roundabout is only a plot of land, a flat circle of greenery raised no higher than curb-height in the middle of radiating roads. But, when traffic approaches, the roundabout grows.
The circle of the roundabout is divided into five circles, one inside another, one attached to the other. The outermost circle is fixed, while the four inner circles are movable: each responds to incoming cars from one of the four roads that head toward the roundabout. When a car passes over a sensor embedded in the road, it sets off a motor that activates the one circle of land directly in front of it.

As you drive toward the roundabout, the roundabout comes to life: the roundabout breathes, the ground opens, a disk of land pivots up in front of you. As the ground splits open, water falls; from under the disk, a waterfall pours down into a pool in the middle of the roundabout; light shines up from under the pool, the waterfall glows. You’re driving into the mouth of the roundabout; you veer off to the side, and circle the roundabout.

Each additional car, crossing the sensor, props the ground further open, to a height of five meters; each additional car after that, then, keeps the ground open, and the waterfall flowing, a few seconds more. As cars approach from more than one road, the roundabout grows: circle upon circle of land pivots open, one on top of the other. The roundabout rises, higher than the elevated highway beside it.
As cars drive away from the roundabout, the land closes, circle by circle; the waterfalls are closed up inside the ground; the roundabout sleeps, ready to wake, ready to tremble, at the first sign of another approaching car.