Ever wonder why traffic jams appear when there is no accident or other apparent cause?
The Mathematical Society in Japan used a test track to replicate traffic jams that seem to occur for no reason. These “shockwave” traffic jams travel backwards at about 20 km (~12 mph). That’s why you don’t always see the massive wreck you expected after sitting in traffic for so long. Something as simple as a miss timed lane change can cause a ripple that creates a nasty “shockwave” backup.
In this video, it starts around 14 seconds in when the white car slows down for a second. The rest would be familiar to anyone who’s driven the freeways during rush hour.