Cars follow simple acceleration, braking and random-dawdling rules on a ring road. Watch phantom traffic jams form from nothing — the same "stop-and-go waves" you experience on real motorways.
Nagel-Schreckenberg model: accelerate if gap ahead is large, brake if it's small, randomly slow down. These simple rules reproduce real traffic phenomena.
Adjust car density and dawdling probability. Watch traffic jams appear, propagate backward (upstream) and sometimes dissolve. High density creates persistent congestion.
Phantom traffic jams travel backward at about 20 km/h — the speed of the "jam wavefront". Japanese researchers reproduced this with cars on a circular track in a famous 2008 experiment.