The Caterpillar Effect

The phenomenon experienced on the road when someone decides to slow down their car to look at something of interest on the side of the road. This causes that area of the road to slow down for the following hours. This leads to cars, collectively, mimicking a caterpillar walking.
The phenomenon is easily observed on highways.

MAN! Some jerk decided to stop and look at one of the millions of car crashes a day and it's making everyone feel the Caterpillar Effect for the next hour!