From Brake Tests to Tablet-Controlled Uncoupling: DAC Trials Redefine EU Rail Logistics

Europe’s FP5-TRANS4M-R project moves closer to authorising Digital Automatic Coupling (DAC), with successful cross-country tests and next-stage plans.

As Europe intensifies efforts to modernise its rail freight sector, the spotlight is firmly on Digital Automatic Coupling (DAC)—a key innovation set to redefine how freight trains operate across the continent. With extensive testing under way through the FP5-TRANS4M-R project, DAC is no longer a concept—it’s fast becoming a production-ready system with significant implications for efficiency, safety, and digitalisation in the rail industry.

Three Countries, One Goal: DAC Testing in Real-World Conditions

Co-funded by Europe’s Rail Joint Undertaking, the FP5-TRANS4M-R project has focused on cross-border demonstrators, lab simulations, and in-service trials to assess DAC's reliability. As Molley Williams, project manager of FP5-TRANS4M-R, explained: "We need to show that we have a robust, reliable, safe product and secure processes. That’s what the tests are for—authorisation."

The testing program took place in Germany, Switzerland, and Sweden, covering installation, interoperability, and coupling procedures. Germany's test lab in Berlin-Spandau served as the foundation, simulating complex technical scenarios in a controlled environment.

Switzerland’s SBB Cargo demo train brought the testing to live tracks. Using Powerline PLUS, a communication system transmitting data via the 400 VAC train power cable, it supported essential digital functions such as automated brake tests, train composition detection, train integrity monitoring, and automatic uncoupling. Over the course of 10 months, the prototype ran more than 4,200 km, covering diverse terrain across Lupfig, Dottikon, Wildegg, and Basel Marshalling Yard.

Sweden’s World-First Commercial DAC Deployment

In a European first, Sweden now operates the first DAC-equipped train in commercial traffic. The intermodal train, managed by SHN Cargo in the south, runs daily under real market conditions. Meanwhile, a heavy steel train in the north, operated by Green Cargo, is also in commercial use. According to Anna Björkman, Program Manager at Rail Sweden, "These trains are essential to understanding DAC performance in extreme weather and heavy-load conditions."

It is a major milestone for the EU, proving that DAC is not just a lab-tested concept, but a field-proven innovation. The data collected is now fuelling the next phase of development, with two additional demonstrator trains planned for Austria and Italy.

DAC Key Functions: From Train Integrity to Auto-Brake Tests

The Swiss demonstrator played a key role in validating the core digital functions of the DAC system under real-world conditions. One major achievement was the successful train composition detection, with the PTB Train Topology Detection protocol accurately identifying the sequence and orientation of all wagons. In terms of safety automation, the automatic brake testing functionality, integrated with PJM’s WaggonTracker, enabled efficient and precise brake assessments, significantly reducing the need for manual checks.

The train integrity monitoring system also delivered promising results, as it effectively detected communication losses via PTB without triggering false alarms, thus meeting expected response time benchmarks. Meanwhile, automatic uncoupling, developed by Voith, proved fully functional—both manual activation via onboard pushbutton and remote control through a tablet interface performed seamlessly during test operations.

🚆 A big step for rail freight automation! 🚆

Successful large-scale tests within our #EU_Rail FP5-TRANS4M-R project have validated the Powerline Train Backbone (PTB) as a robust communication system for Digital Automatic Coupling (DAC). ✅

🔗 //t.co/s6chZiETNX pic.twitter.com/nVAkW2RS1y

— Europe's Rail JU (@EURail_JU) April 3, 2025

What Comes Next for DAC: Scaling, Standardisation, and Interoperability

Looking ahead, the project is now prioritising system integration and preparing the DAC for full-scale production. Central to this effort is the finalisation of functional safety standards, a key requirement for EU-wide certification and adoption. The team is also working on enhancing the onboard power supply to ensure robust wagon-level autonomy, especially in challenging operational environments. Another area of focus is improving the stability of insulation resistance, which is essential for consistent performance across diverse weather conditions.

These development steps are being carried out in alignment with the CENELEC standardisation process and EU-Rail’s System Pillar programme, both of which aim to ensure that DAC becomes a truly interoperable and harmonised technology across Europe’s rail freight network.

Sources: Europe's Rail; Rail Sweden