What causes traffic jams

Congestion research

In sync

Actually there is enough space on the motorways. And even if a speed limit of 60 applies on a construction site - if everyone drives at this speed, then it should also proceed at this speed.

Experience shows, however, that even small obstacles can cause large traffic jams, that even traffic jams can arise, although not a single disruptive factor is hindering the motorcade. The traffic jam out of nowhere seems to be a big mystery: No accidents, no construction sites or objects on the road - and yet a traffic jam suddenly arises in relatively dense traffic.

Traffic researchers have long since discovered the secret. The "traffic jam out of nowhere" is caused by a handicap: namely the psyche of the ordinary driver. He reacts too slowly and often too strongly. A small braking maneuver by the vehicle in front is reinforced by the vehicle behind it and then again by the next.

This creates a traffic jam that continues to the rear - and at a precisely predictable speed: The traffic jam runs backwards at 15 kilometers per hour and everyone is caught - except for the driver who actually triggered the traffic jam.

The traffic researchers are looking for solutions to prevent these and other traffic jams. It would be ideal if all vehicles could start and brake at the same time. The human driver is largely unsuitable for such maneuvers - but the computer can do it.

In experiments, scientists experiment with trucks that are electronically connected to each other. The vehicle in front is driven in the conventional way, while the vehicle in the rear is attached to an electronic rope and automatically reproduces all braking and driving movements of the vehicle in front. Such a technology could avoid traffic jams if a sufficient number of vehicles were equipped with it.

However, the technology is not yet sufficiently developed to be ready for the market. Automatic spacers, on the other hand, are already possible: the vehicle recognizes the vehicle in front and reacts if the driver does not do this himself. Up to now, such distance sensors have only played an indirect role in avoiding traffic jams: they help to avoid accidents.

Cell phone as traffic jam alarm

But there are other aids to escape the daily traffic jam: Most vehicles have long been equipped with navigation devices - and most of them have a TMC system on board. TMC stands for "Traffic Message Channel" and processes all information that is broadcast via the traffic channels.

In this way, the driver can see in advance whether he is approaching a traffic jam. The system can then suggest alternative routes. This works as well as the traffic news is. The traffic jam report from the transmitter can never be precise.

A reported traffic jam may have cleared just as the driver passes the point; another can arise before the TMC receives the corresponding message. TMC systems are often only of moderate help, especially for shorter distances.

In the late 1990s, the industry began developing a successor to TMC. This got the same name as the group of experts who developed it: TPEG (Transport Protocol Experts Group). The developers assumed that the digital radio standard DAB (Digital Audio Broadcasting) would spread rapidly.

DAB should enable detailed traffic information to be sent to drivers more quickly. But information on delays in local and long-distance public transport should also be disseminated.

However, the expert group found that their project was too complex to be put into practice. All that remained of the idea was a data protocol called TPEG, which many manufacturers still use for their navigation devices today.

Is the collapse coming?

But traffic jams can also be avoided with simple technology. Paradoxically, due to the standstill of some vehicles: traffic lights can help prevent traffic jams. For example at the motorway access roads. With the help of these so-called inflow controls, the traffic planners ensure that the flow on the motorways is maintained and that constant movement is not interrupted.

Although the individual driver has to wait a few seconds to get onto the motorway, the time lost is in no relation to the minutes or even hours lost that would be caused by a traffic jam caused by excessive traffic at individual points.

The volume of traffic is growing, but the options for expanding the road network are limited. This is why research into traffic jams is becoming increasingly important - only through intelligent systems can the traffic collapse be avoided within the next 20 years, or through a fundamental change in our traffic behavior.

Almost 90 percent of private journeys are still made by car. Switching to bus and train is too cumbersome for many travelers, but it is still the best way to avoid traffic jams for yourself and others.