VGF and Siemens Mobility have announced progress in the testing of a semi-automated subway prototype as part of Frankfurt’s Digital Train Control System (DTC) project. Over the past year, a modified "U5" train has been operating on a test track at VGF’s central depot. The project uses Communications-Based Train Control (CBTC) technology to allow trains to communicate continuously with infrastructure, enabling partially automated operation under driver supervision.
Starting in 2027, VGF plans to begin gradually updating its current train control system to CBTC. This upgrade will introduce a "moving block" system that maintains safe braking distances between trains rather than relying on fixed sections of track. As a result, trains can run more frequently without the need for new tracks or stations. The company expects this to increase service reliability and schedule accuracy while reducing energy consumption by up to 25 percent and minimizing wear on vehicles and tracks.
Wolfgang Siefert, Head of Mobility, stated: “I am pleased that the DTC digitalization project has reached this milestone, and we will now see in practice what we’ve been discussing in theory for years. This is good news for Frankfurt: The automated prototype tests show that the digital transformation can drive urban mobility. Specifically, DTC will make public transportation more efficient, reliable, economical, environmentally friendly, and even more comfortable.”
The integration of CBTC with other traffic management systems is also underway. Since some metro lines operate above ground, DTC has been connected with Frankfurt’s MIND(+) initiative—an urban project using Cooperative Intelligent Transport System (C-ITS) technology to coordinate railways, trams, and road traffic. The successful test linking CBTC and C-ITS was conducted on VGF’s test ring.
VGF Managing Director Steffen Geers said: “We are pioneers here and the first transport company worldwide to connect these two technologies. For VGF, DTC is one of the most important innovation projects, and a technology with which we will be future-proof for years to come.”
Guido Rumpel, Head of Rail Infrastructure Germany at Siemens Mobility added: “With our modern CBTC technology Trainguard MT, we are making Frankfurt’s public transport fit for the future. Trainguard MT enables more trains to run at shorter intervals through semi-automated operation. This provides up to 30 percent more capacity with technically possible train sequences of less than 100 seconds, increases energy efficiency, and significantly improves punctuality. This technology has already been proven in cities such as Paris, New York, and Singapore – and it is now being used in Frankfurt.”
Currently installed on tunnel sections of lines U4 and U5 between Bockenheimer Warte and Seckbacher Landstraße, static system tests are scheduled for September and October 2025; passenger-free trial runs are planned for January 2026. Completion of lines U4 and U5 is targeted for 2027; additional routes including A-Route (lines U1-U3/U8), C-Route, and tram services will follow by 2033.
VGF operates Frankfurt’s nine metro lines and ten tram lines across over 133 kilometers of track. In 2024 it transported over 182 million passengers with approximately 400 rail vehicles supported by over 2,800 employees.
Siemens Mobility is an independent entity within Siemens AG focused on intelligent transport solutions such as rolling stock manufacturing and rail automation systems worldwide; it reported €11.4 billion in revenue during fiscal year 2024.
Both organizations view these technological advancements as key steps toward creating sustainable urban mobility solutions that prioritize efficiency while reducing environmental impact.