In large cities, countless drivers spend a large part of their time at red traffic lights. Hackers have now succeeded in building devices that can be used to switch the traffic lights in many municipalities.

The traffic lights in many German cities work with hopelessly outdated radio technology. This ensures that the signals can theoretically be manipulated by any driver. This was found out by IT specialists who published their results together with “Heise”, NDR and BR. The NDR warns: “Artificially extended traffic light phases could create traffic jams or cause chaos.”

Radio signals from the eighties

The hackers take advantage of the so-called traffic signal system influence. This is a technology from the 1980s that allows buses to move through traffic with fewer forced breaks and thus better adhere to timetables.

It works like this: A bus approaching a traffic light announces itself there. The traffic light then changes its switching times and extends a green phase or pulls the transit signal ahead of schedule. An unencrypted, analog radio signal has been used to communicate between the bus and the traffic light for more than 40 years.

Although this signal is transmitted on frequencies specially reserved for this purpose, on which private devices are not allowed to transmit under any circumstances, the system is still vulnerable. But because even the demonstration of the IT specialists is punishable, they are not named by the cooperating media – the main concern is the warning that many traffic lights are apparently a weak point in the public infrastructure.

In an article by NDR, the experts show how easy it is to switch between the light signals with a laptop. The hackers ride in a car with the journalists and roll towards a red light. Pressing the “Enter” key on the appropriately equipped laptop triggers the signal – and the traffic light switches to green. The effectiveness of this technology is demonstrated several times in the program “Panorama 3”.

Limited chaos conceivable

After all: It is apparently not possible with radio technology to grant free travel in all directions at an intersection or to switch off traffic lights. But the hacker warns that traffic jams can of course be caused by constantly switching the signal in one direction.

After the demonstration, the reporters asked several cities which technology was used for the traffic lights there. The result: modern technology is rather the exception, around 80 out of 100 cities rely on the tried and tested, but now very old radio signal. The NDR writes: “Upon request, many cities admit that the system can be exploited. The possible effects are low, they say, and it is also very complex and prohibited. No city is aware that the signal was ever intentionally exploited.”

In the ears of the experts, that might not sound very convincing – after all, someone who wants to cause damage does not necessarily comply with prohibitions. However, many cities are reluctant to make the switch. The reasons given are not enough staff and high costs for converting vehicles and traffic lights.

Fortunately, analogue radio, as used here, has an expiry date. The cities must switch by the end of 2028 at the latest, after which the unencrypted signal may no longer be used. So far, only a few cities have reacted in advance. It is said that the hackers only have no chance in Kempten, Heilbronn, Cologne, Dortmund, Bonn, Passau and parts of Hamburg. Free travel applies to the rest – for anyone who uses the technology illegally.