If you’ve spent any amount of time on the road in one of South Africa’s major cities you would have undoubtedly been in a traffic jam that seemed to appear out of nowhere.
There were no accidents, no broken down cars, and no hazards on the road that could impede the flow of traffic, yet, here you were, gridlocked on a major freeway for no apparent reason.
After some time, at an arbitrary point on the road, cars just start accelerating again and all of a sudden you’re no longer stuck at 20km/h.
The phenomenon is what’s called “shockwave traffic” and can be the ripple effect of just one driver’s actions.
What’s the deal with shockwave traffic?
A Japanese experiment conducted by the University of Nagoya at the turn of the century shone a light on how shockwave traffic jams usually form.
The researchers placed 22 cars on a circular track and instructed the drivers to keep a set speed of 30km/h while going around.
At first, everything went smoothly and the cars remained relatively equally spaced from one another as one would expect.
However, due to individuals reacting at different speeds both physically and mentally, and vehicle speedometers being calibrated differently, the following distances soon started to vary from one car to the next.
As a result, some drivers were forced to tap the brakes to give space to the cars in front of them, causing the cars behind them to bunch up and create a traffic jam.
The jam spread backwards around the track like a shockwave at around 20km/h, accurately mimicking real-world scenarios in which traffic forms at about the same speed.
The first-of-its-kind study perfectly illustrated why traffic jams sometimes appear to have come out of absolutely nowhere, no matter where you’re driving in the world.
A video of the experiment, published to YouTube by New Scientist 17 years ago, can be viewed below:
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