“Siren” project: Green wave and intelligent routes for rescue workers

Blue light forces such as the fire brigade and police should in future reach their destination faster and more safely. The German Aerospace Center (DLR) has developed and tested an intelligent traffic light control together with users and partners from industry and research in the “Sirene” project.

One of the aims of the initiative was to develop solutions for the privileges of emergency vehicles along green waves. In addition, those involved worked on a smart navigation system that also includes short-term traffic changes in route planning. The Federal Ministry of Transport and Digital Infrastructure funded Sirene with 2.57 million euros as part of the mFund innovation initiative. The state share was 78 percent.

The The project ran from 2017 to 2020. The DLR has now presented the first results. “You sit in the car, see the blue light, hear the siren and ask yourself, where should I go?”, Said project manager Sten Ruppe from the DLR Institute of Transport Systems. “Instead of stopping all the traffic, we can use the siren technology to prioritize with pinpoint accuracy and direction.”

“We only switch the traffic lights red that we need,” says Ruppe, explaining the approach. “In this way, we can also block individual directional lanes that are then used by the rescue services to overtake.” Conversely, this means: “The traffic on other lanes, which does not affect the route of the emergency services, can continue uninterrupted. This way we can prevent a lot of traffic jams.” According to the helpers involved, the process has proven itself particularly at highly frequented intersections and “massively defused” the dangers lurking there.

In practice, the team tested the green wave for rescuers at 16 intersections in Braunschweig. For this purpose, three fire engines and an ambulance were equipped with the siren system. In addition to LTE mobile communications, the most important component was Car2X communication, in which vehicles exchange information with each other or with the traffic infrastructure, for example in the form of traffic lights. The aim is to create “Cooperative Intelligent Transport Systems” (C-ITS), which the EU Commission has long wanted to promote.

The emergency vehicles were able to influence the traffic before they reached the intersection. During the trial run, the siren system was also connected to the traffic control computer of the city of Braunschweig, the fire brigade’s control system and the traffic lights. “If an alarm message is received, the routes for the emergency vehicles are calculated,” is how the DRL explains the principle. As soon as you get into the emergency vehicle, the route is created and displayed on a screen.

In the course of the test, the partners tried out various methods of controlling the traffic lights. Once the system registers the emergency vehicles via the city’s central traffic control computer. When leaving the fire station, the siren switches the respective traffic lights to red for other participants directly via the traffic control computer and prioritizes the passage for the emergency vehicle. This solution was largely built by the companies PTV (Transport Transport Planning) and Gevas Software, which specialize in traffic informatics. The company Afusoft Kommunikationstechnik was also on board.

The second option: If an emergency vehicle approaches an intersection along the route that is further away from the fire station, the traffic light is controlled decentrally. One or more vehicles register at the intersection using a Car2X solution programmed by DLR. Sirene then decides on the respective privileges depending on the situation. Once all emergency vehicles have crossed an intersection, the system automatically releases the prioritized traffic light switching.

According to Ruppe, the continuous and exact position reporting of every emergency vehicle and high speed in processing and forwarding data are crucial. Overall, this avoids unnecessary waiting times for the other road users. It has not yet been decided whether the process should be used on a larger scale and in the long term.


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