Phantom Traffic Jams
Stop-and-go waves emerge spontaneously above critical density
Cars: 30
Avg Speed: 0.0
Jams: 0
Phase: free flow
Phantom traffic jams (Nagel-Schreckenberg model, 1992) arise from driver overreaction: a slight braking propagates backward as a stop-and-go wave, moving opposite to traffic flow at ~15 km/h — even with no bottleneck or accident. Above the critical density (~30 cars/road for this ring), small perturbations are amplified into persistent jams. Below it, flow is stable and free. The jam is an emergent, self-sustaining wave: each car that enters the jam eventually escapes the front, but the jam itself travels backward indefinitely.