Traffic Flow Dynamics (2D): Ring-Road Car-Following Model

This 2D companion drives the same "traffic flow" idea as the 3D version through the actual physics literature uses to explain it: the Optimal Velocity car-following model on a closed ring road. Every car continuously relaxes its speed toward a target set only by the gap to the vehicle ahead, and at high density or low driver adaptivity that feedback loop goes unstable on its own — no crash needed — producing the same self-sustaining stop-and-go shockwave measured in real ring-road experiments.