From Pilot to Practice: Digital Automatic Coupling Tested on German Freight Trains

The journal VDVmagazin, published by the Association of German Engineers and Measurement Technicians, has released a detailed report on the ongoing testing of Digital Automatic Coupling (DAC) on German railways.

RAILTARGET has been reporting regularly on DAC testing in Europe, including recent trials under extreme conditions.

The specialist magazine presents an in-depth account of DAC testing on a freight train operated by the Westphalian State Railway (WLE), consisting of twelve fully loaded freight wagons hauled by a 2,000 kW diesel Eurorunner locomotive. The tests were deliberately conducted on a rugged, hilly route in the federal state of North Rhine–Westphalia. For readers outside the rail sector, the report explains how a DAC-equipped train differs visually from conventional rolling stock, most notably through the absence of the traditional two buffers, replaced by a centrally mounted digital automatic coupler aligned with the wagon axis.

"DAC represents a revolution in rail freight transport," Fabian Wartzek, DAC project manager at Deutsche Bahn AG, told VDVmagazin. Subsidiaries DB Cargo and DB Systemtechnik are acting as project partners to WLE in the automatic coupling tests, which are organised and co-financed by the EU rail industry body Europe’s Rail under the DAC4EU programme.

Testing Under Real-World Freight Conditions

The trains operate up to five times per day, transporting limestone over a 60-kilometre route between a quarry near Warstein and a cement plant in Beckum. A total of three trainsets are deployed. Initial testing began in March 2025 on the first two pairs of Fa wagons. By early November last year, six automatic couplers had been installed and placed into daily operation. "So far, our DAC-equipped wagons have covered nearly 20,000 kilometres," said Felix Holtmann, WLE’s rail operations manager. "There were no issues with limestone dust, and we recorded no dents or cracks on the DAC — everything functioned flawlessly."

Fully Digital Freight Trains to Enter Service This Year

Launched in 2020, the DAC4EU project has now entered its sixth and final phase. After more than four years of development and testing, the programme is moving towards "operational testing in real-world conditions." The current trials are based on couplers supplied by Voith, with DAC equipment being installed at WLE’s workshop facilities. Freight wagons and locomotive couplers are prepared there, with power and data cables already installed in the wagons, although not yet activated.

During the trial phase, digital and electrical components will be connected at a later stage. This creates readiness for a future upgrade that will transform the automatic coupler into a fully digital automatic coupling system. At the Warstein site, trains must currently be split into two sections for loading. With DAC, decoupling will be possible at the push of a button, and brake systems will be tested automatically. "DAC delivers a massive reduction in workload for shunting staff and significant time savings during train formation," Holtmann said.

Testing parameters for the digital coupler are particularly stringent due to the nature of the transported materials. Limestone for the cement industry is loaded from above, and stray fragments can fall directly onto the coupler. In addition, tests examine how aggressive limestone dust contaminates DAC components. "This inevitably leads to higher maintenance requirements for couplers and buffers," explained Ole Lebek, who is responsible for vehicle technology development and maintenance at WLE.

A major challenge is the low mountain range that freight trains must cross on the route between Warstein and Anröchte. The line follows the slopes of the Haarstrang ridge, featuring steep gradients and tight curves, climbing to an altitude of 330 metres before descending again. Its most striking section is known as the Westphalian Semmering, named for its resemblance to Austria’s famous mountain railway — Europe’s first standard-gauge mountain line. Between Warstein-Belecke, Uelde and Anröchte, heavily loaded freight trains must overcome an elevation difference of around 250 metres over a distance of 20 kilometres, with some services requiring banking locomotives.

WLE manages its own rail network spanning approximately 120 kilometres and transports more than one million tonnes of goods annually, primarily limestone and cement, as well as beer and timber. Freight trains equipped with DAC are not yet permitted to operate on the federal rail infrastructure, as German rail authority regulations prohibit real-world DAC testing on the DB InfraGO network. However, testing is permitted on non-federal infrastructure such as WLE’s network, particularly due to the yet-unapproved DAC hardware. Federal rail inspectors remain actively involved throughout the testing process.

"The Europe-wide deployment of DAC represents a major step towards the modernisation and digitalisation of rail freight transport, creating long-term potential to strengthen its competitiveness," said Dominik Knoop, Head of Rail Technology at the Association of German Transport Companies (VDV). "It is essential that DAC demonstrates reliability before large-scale deployment and is ultimately designed to be user-friendly and compatible with the business models of rail freight operators."

Traditional couplers have been in use on railways for nearly 150 years, with coupling and train formation involving significant manual effort and safety risks for staff. In its report Transport Transition and the Concept of Quieter Rail Transport by 2030, Germany’s Federal Environment Agency also highlights DAC as a response to labour shortages and the declining number of young entrants into rail professions such as shunting.

Source: VDVmagazin