Odds Are You Are Responsible for that Traffic Slowdown

I know, potentially insulting readers in the headline is not a good way to keep people interested, but it’s statistically true. Until recently, when stuck in bad traffic I daydreamed about having a  drone or helicopter view to see where the problem is. On occasion I am close enough to the front of the jam to see the cause; absolutely nothing. I’m sure plenty of folks will immediately recognize this having seen it themselves. 

So what’s the actual cause? Basically a single person isn’t paying attention and they brake or decelerate enough to cause the initial slowdown. This causes everyone behind them to slow down as well. The real issue is that when traffic picks back up, everyone is slow to accelerate back to speed. It causes a repeating pattern where every single person fails to accelerate quickly. They are apparently dubbed “shockwave” jams.

Recently, researchers from several Japanese universities carried out a very simple experiment to clearly demonstrate the phenomenon. I love that it is such a simple experiment involving just 22 vehicles on a circular track. Drivers were instructed to drive 30 kilometers per hour (18.6 MPH) around a 250 yard track and it didn’t take long before the shockwave jam began. No surprise it was human-created. If you really want to get into the weeds of the research, check out the paper “Traffic jams without bottlenecks—experimental evidence for the physical mechanism of the formation of a jam”.

“If they had set up an experiment with robots driving in a perfect circle, flow breakdown would not have occurred. Human error is needed to cause the fluctuations in behaviour,” – Tim Rees,  TRL (UK transport research firm)

As part of the results, the researchers posted a video of it on YouTube. Just 39 seconds but it is very informative. The solution to these shockwave jams? Hit the gas and speed up quickly to get back to the speed limit as fast as possible. If everyone on the road does this, the shockwave will dissipate fairly quickly. Then staying more aware while driving will help prevent the next one.