Will we ever solve problems with highway traffic?

The three main theorems of traffic jam research: the butterfly effect, invisible waves (= phantom traffic jam) and the tragedy of chance

There are many different reasons for congestion. Most obvious to us are construction sites, accidents and the so-called elephant races, in which one truck overtakes another, supposedly slower, truck. Due to the speed limit of 80 km / h and the small speed difference, a comparatively long time is required for overtaking.

However, these are by no means the most common reasons why a traffic jam occurs.

The main problem with traffic jams is a saturation problem. There is only a certain limited amount of space available for cars on a kilometer of road. Typically, the capacity of a road is 1500 to 2500 vehicles per hour per lane when the vehicles are moving at a speed of 80-100 km / h. Driving faster and slower will reduce capacity. The problem of saturation begins when the demand for that space is greater than the space available. Around 50 percent of traffic jams are caused by congestion on the road network.

Demand peaks over the day (morning and evening rush hour) and over the year (holiday season) meet a rigid supply. The road capacity cannot be increased in the short term; the network section is overloaded. An expansion of the road also only alleviates the problem for a short time, as the demand adapts to the expanded supply. The expansion of the road will reduce the amount of traffic jams in the short term, the time required for a certain network section and the associated time costs will also decrease. Since every road user subconsciously weighs up several options with regard to the choice of means of transport and route, he comes to the conclusion after the expansion that the previously congested route has become more attractive due to the expansion. Like all other road users, he will prefer this route to alternative routes until the previous situation is reached again with the corresponding volume of traffic jams. Only through the traffic jam and the corresponding loss of traffic jam time are the route's evaluation changed again and other means of transport or routes taken into account.

In addition to the voting behavior of road users, three other effects have a very strong influence on traffic jams: the butterfly effect, invisible waves (= phantom traffic jams) and the tragedy of chance.

The butterfly effect or "traffic jam out of nowhere"

The theory of the butterfly effect assumes that a single driver can be responsible for a traffic jam. His behavior triggers a chain reaction that takes place as follows:

If you brake, overtake or perform another driving maneuver, a traffic jam can arise many kilometers and minutes later.

Example: On a busy motorway, driver A drives at 120 km / h. Since he wants to overtake another vehicle, he pulls into the lane on the left of the vehicle. The cars of driver B and driver C driving there, which were also traveling at 120 km / h, have to reduce their speed to 100 km / h in order to let driver A thread into their lane. Of course, all other drivers behind drivers B and C also have to reduce their speed to less than 100 km / h in order to avoid a rear-end collision and to maintain the necessary vehicle distance. Excessive braking continues like a chain reaction and increases from vehicle to vehicle until a first vehicle comes to a standstill. A traffic jam arises out of nowhere.

In addition, there is a time delay in the resolution of a traffic jam. One to two seconds pass before a driver starts his vehicle again at the front of the traffic jam and clears a street length of 5 to 10 meters. Thus, the front of the traffic jam moves against the direction of travel at a speed of around 15 km / h. Traffic jams occur in downstream sections of the route, although the original cause of congestion has already been removed in another section of the motorway.

In order to protect your personal data, the loading of the YouTube video and the associated data transfer to YouTube have been blocked.
click on Load videowhen you want to view the video.
By calling up the video, you accept YouTube's data protection conditions.
You can find information on this here: Google - Privacy & Terms.

Load video

This effect can only be stopped if all vehicles can always drive at a constant and identical speed. Since this is not the case due to the human factor, traffic jams will arise again and again.

In an investigation by the University of Cologne, four human causes of error were found:

  1. Driving up too close, which can cause the first and all following cars to brake suddenly,
  2. Unlocking too quickly and, as a result, braking just as quickly and
  3. mentally under-challenged in slow-moving traffic to keep a sufficient distance, because the drivers wander with their thoughts.
  4. counterproductive driving in order to move faster on the lane with supposedly more flowing traffic (jumping in columns).

The above verbal formation of a “traffic jam out of nowhere” or “phantom traffic jam” was mathematically formulated in 1992 by the physicists Kai Nagel and Michael Schreckenberg in the so-called “Nagel-Schreckenberg model”:

Given a specific number of vehicles, represented by the number