Phantom Traffic Jams Explained

However, don’t start blaming snow for causing such blockages, because drivers are those creating them and we’re not necessarily referring to crashing their vehicles in the middle of the road.

Although this has been discussed before, a team of scientists and mathematicians have proven it’s the drivers' fault and their way of driving for creating slow traffic flow or even jam it completely for longer periods.

Braking and distance

With enough cars on a highway it takes only a minor disruption to slow traffic down and create a chain reaction that builds up and becomes a wave of high vehicle density, which usually results in a jam.

The process is pretty simple:

• You have a flock of relatively similarly distanced cars going at the same speed
• One of them needs to brake because of a road irregularity or some stupid thing someone did up front
• Braking will force each of the other cars behind to slow down as well
• Some drivers could overreact and brake even harder, not understanding why everyone upfront does it and wanting to be safe
• The others behind will think the same and eventually this will lead to a full stop on a certain segment
• Drivers up front will realize there’s nothing to be afraid of and will slowly start driving away
• Some might even change lanes thinking there could be an accident somewhere, slowing everything down again and again

And there you have it, people standing in line for nothing, just because someone had to brake a bit more up ahead and created a massive braking wave behind.

This could be avoided in some ways if everyone would keep enough distance between automobiles while going down the highway and brake only if necessary. But then who would also put on makeup, send text messages, talk on the phone and fiddling around while not paying attention to the road ahead?

Even when vehicles start leaving the traffic wave, this doesn’t disappear, but drift backwards, against the direction of the traffic flow.

"It's typically 100 to 1,000 meters long, and it usually begins with vehicles running into a sudden increase in density at the start, and a drop in velocity," Temple University mathematician Benjamin Seibold explains. "Then, after that, they slowly accelerate again."

You can see it happening in the video bellow as recreated some time ago by Japanese researchers with only 22 cars and their drivers being instructed to do only two things: maintain the same distance between cars and a speed of 11.5 mph (18.6 km/h).

Not convinced yet? Check out this neat online traffic simulator here to see how the phantom traffic jam gets created and carried over at a larger scale.

Solving the problem?

As Seibold said, “if people anticipate higher traffic densities ahead, and take their feet off the gas earlier and leave more room in front of them — instead of waiting until they have to brake — that can prevent traffic jams from arising.”

However, that’s hard since you can’t educate that many people to have driving manners and at least someone will find it cool to tailgate somebody else and brake violently after to create the slowdown.

This means, the only measure we can implement is autonomous cars and smooth, safe highways that eliminate the necessity to brake. Self-driving cars that can “talk” to each other will be smart enough to maintain a precise speed and distance while also being “aware” of what’s up ahead and brake only when absolutely necessarily.

It all revolves around discipline and since we can’t have nanny state authorities watching everyone and punishing them for each transgression, the only way we can eliminate phantom traffic jams is to rely on future technology. Or stop driving cars at all if not necessary; they’re way too many out there anyway.