> like how people slow down to view a car crash when they're driving by. Or they slow down because the crash causes them to doubt the condition of the road; th

> like how people slow down to view a car crash when they're driving by. Or they slow down because the crash causes them to doubt the condition of the road; there may be debris strewn around they need to avoid. A lane may be closed too. When a road is saturated to capacity, anything that gets people to slow down a little bit will cause a chain reaction that snowballs into a full traffic jam. Even slight perturbations without lane closures can cause traffic jams: https://www.youtube.com/watch?v=7wm-pZp_mi0 https://www.youtube.com/watch?v=7wm-pZp_mi0