Where Do Traffic Jams Come From? The Science Behind Phantom Traffic Jams and Why Congestion Appears from Nowhere

Rush hour on the Accra--Tema Motorway. People are driving home after work. Traffic is heavy, but it is moving steadily. Then, without warning, the vehicles ahead begin to slow down. Before long, traffic is moving at walking speed. Drivers look ahead, expecting to see a crash, roadworks, or a broken-down vehicle. Some change lanes, hoping to make faster progress. Others simply wait. After several minutes, the vehicles ahead begin to move. One by one, drivers pick up speed as they make their way through the queue. When they finally reach the point where traffic first slowed, they find something surprising. The road is clear. There is no crash, no broken-down vehicle, and no roadworks. Many of us have experienced this. We leave asking the same question: If nothing was blocking the road, what caused the traffic jam?