The Science Behind Traffic Jams
A particularly nice graphic that explains (at an extremely high level) what causes traffic jams. The root cause is a combination of saturation and what’s called a Backwards Travelling Wave. A simple event such as a lane change causes cars behind to slow slightly and every subsequent line to slow further in order to maintain safe distance. The further away from the original event a car is, the slower it will have to go to avoid hitting the cars in front.