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Around the World with Yunex Traffic: Germany

Digital Train Control System for Frankfurt’s Subway and Tram Systems

The authority for public transport in the city of Frankfurt, Verkehrsgesellschaft Frankfurt (VGF), will replace its conventional train control system previously used in the subway and tram sector with a new, modern and digital system. The “Digital Train Control System Frankfurt” (DTC) project is one of VGF’s most important projects for the future.

Systems such as the “Digital Train Control System Frankfurt” are referred to in the industry as “Communication Based Train Control” (CBTC). CBTC is a complex system of digital signals and messages that permanently exchange information between vehicles and track in real time. Various components on the track and in the vehicles make this radio-based, bidirectional data communication between train and infrastructure possible, in which track information is transmitted to the trains via radio system.

By 2031, the entire VGF network is to be converted to digital train control, initially all nine lines of the subway system, then the ten tram lines. The first of these will be the “B line” with the U4 and U5 lines, including the U5 extension to the Europaviertel, which – according to the current plan – is to go into operation with DTC train protection in 2025.

“The digitalization of train protection with ‘DTC’ is a project that will not only gain outstanding importance for Frankfurt’s public transport system in the coming years, but with which the city and VGF will be leading the way nationwide,” said Director of Transportation Department Stefan Majer about the project (VGF, 2021). DTC Systems such as the “Digital Train Control System Frankfurt” will be introduced in a German city for the first time. With this technology, subways and trams will be connected to each other via telecommunication and digitally linked in real time. Trains can thus run at shorter intervals, which in turn makes it possible for the VGF to significantly expand services without having to rebuild or reconstruct lines or stations.

Teamwork makes the dream work

Together with Siemens Mobility, we at Yunex Traffic are implementing the above-ground DTC system and are equipping both trains and the rail line with its own cooperative technology. Central elements are Onboard Units (OBU) and Roadside Units (RSU) which, in interaction with the CBTC systems from Siemens Mobility, exchange information between infrastructure and vehicle. For the total of 675 trains in Frankfurt, the Yunex Traffic OBU is being redesigned for industrial use in a train. More than 160 RSUs will be installed on a total of 43 kilometers of the rail network in Frankfurt, adapting traffic-networking applications (V2X) from the road to the tracks. Both traffic signal systems, level crossings and individual switch controls then communicate and control via RSU and OBU, providing feedback to the CBTC system with up-to-date information. The train driver is provided with the various data via the monitor of the CBTC board computer.


To ensure continuous data exchange, component monitoring and operational monitoring, a cooperative management system is also established. This higher-level system consists of the two control centers CMS (Cooperative Management System) and Sensus from Yunex Traffic, which enable the data flow in the background system of the VGF control center.

In a later project, the same telecommunication technology will also be used to implement smart public transport prioritization of trains at traffic signals in the intersection area. This means that the OBUs of the public transport vehicles (streetcars) communicate with the traffic lights via the RSUs. In addition, information on the ideal departure time at stops or a speed recommendation is displayed to the train driver to be able to pass crossings without having to stop. This is important to maintain the higher train frequency achieved by the CBTC system in the underground also on the surface.