You’ve traveled on a highway. Traffic grinds to a halt and eventually comes to a standstill. After a few seconds, the vehicle starts to move again.
While driving along in a car, on a road, you come upon a large number of stopped vehicles. There are no apparent breakdowns, no accidents, and nothing else to explain this. You’re baffled as to how this traffic bottleneck came to be.
You push the brakes of your car as soon as the vehicle in front of you hits the brakes. It’s possible that the brake lights in front of you just flashed for a brief period of two seconds. When the car ahead of you releases his brakes and you release yours, the process might take you only four seconds to get back to cruising speed. Although it took only two seconds more to get back to cruising speed there is a lag. It may take up to six seconds for the motorist in front of you to regain their usual pace. It might take 8–10 seconds for the car in front of him. This is growing at an exponential rate. And in each case, there is a lag created. This is a chain reaction which magnifies with each car.
It was discovered, by physicists, in the early 1990s that flow is steady below a certain density of automobiles on roads. There is no impact from little disturbances that cause drivers to tap their brakes. Smooth flow is the technical term for this condition. However, as soon as you cross the threshold, the flow of traffic becomes unpredictable. The effects of even the tiniest disturbances may have a huge impact. That’s a jammed flow state. There occurs a phase transition when the flow suddenly shifts from smooth to jammed in a few seconds.
As rush hour approaches, the number of vehicles on the road is approaching a tipping point. When there is a slight snarl or congestion, a few additional automobiles on that stretch of road might trigger a pileup.
Phantom jams are delays that occur out of nowhere and have no obvious explanation. They have been proven by experiment as well as by meticulous observation. Researchers in Japan recorded the movements of automobiles within the Nagoya Dome and the stadium’s indoor baseball pitch in 2013. When the number of automobiles hits a certain level, spontaneous jams began to form.
We tend to assume that a single motorist is at fault for most of these accidents. The models, on the other hand, illustrate that even if everyone follows the laws and does nothing wrong, these waves may still occur.