Space–time: road across, time downwards. Jams are the red bands drifting left.
Flow–density diagram. Dashed triangle: the no-dawdling model. Dots: what this road has actually carried at each density.
Cars per cell. Changing it adds or removes cars without disturbing the rest.
Chance per step that a driver eases off by one cell per step for no reason.
Cells around the ring. Changing it rebuilds the road.
Click a car on the ring to make it brake. Sweep density walks the density from 0.02 to 0.98, holding each value long enough to measure the flow, and fills in the diagram. Shortcuts: Space pause, . step, B brake a car, R reset, D sweep, [/] previous or next regime.