Why Traffic Jams Happen (with LEGO Cars)

​In this video, I build a circular road system with 22 LEGO cars to recreate real traffic flow and find out when traffic suddenly breaks down. Each car is programmed to behave like a human driver, reacting to the distance of the car in front by braking and accelerating.

By gradually adding more cars, a surprising result appears: at a certain point, traffic becomes unstable and a traffic jam forms out of nowhere.
I also tested different types of drivers, including normal human drivers, distracted drivers, and self-driving robot cars. The results show how even small differences in behavior can completely change the flow of traffic.
The system uses a magnetic guidance mechanism inspired by Miniatur Wunderland, where vehicles follow hidden steel tracks inside the road.

This experiment is inspired by the famous traffic flow experiment by Yuki Sugiyama.