photo: Dellner DAC Leaflet/DAC
The Digital Automatic Coupling (DAC) project has long been heralded as a key step toward modernising Europe’s rail freight system. But as deadlines approach and technical trials lag behind expectations, some are now asking: Is DAC truly feasible—or is it another ambitious project buckling under its own complexity and cost?
DAC is intended to replace traditional screw couplings with an advanced system capable of mechanical, pneumatic, and digital connection between freight wagons. Its full deployment is expected to boost rail capacity, enable automated brake testing, improve workplace safety, and allow for real-time data transfer between vehicles. At the European level, DAC is positioned as a pillar of the Green Deal. "To meet the EU’s targets of shifting 75% of freight from road to rail by 2050, we must digitise," reads a common refrain in Brussels. But while the theory is bold, the implementation remains riddled with uncertainty.
DAC Costs Far Exceed Estimates
Initial projections suggested DAC upgrades would cost between EUR 5,000 and EUR 17,000 per wagon, according to the European DAC Delivery Programme (EDDP). However, recent evaluations from Central and Eastern European stakeholders place real costs closer to EUR 40,000–45,000 per wagon, especially when including digital systems and installation.
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A joint warning issued by rail freight associations from the Czech Republic, Poland, Germany, Slovakia, and Hungary states: "Total costs have been consistently underestimated. The scope of retrofit required for full functionality is far broader than assumed." The German federal study released in 2024 supports this concern, suggesting that even the pilot phase of 1,600 wagons and 95 locomotives may cost around EUR 200 million, with full implementation in Germany alone estimated at EUR 8 billion—likely an understatement, as it does not fully include infrastructure adaptation or long-term maintenance.
The Infrastructure Gap
A recurring critique in implementation strategies is the lack of investment in infrastructure adjustments. While DAC promises longer, heavier trains, the existing network often lacks the capacity to accommodate them. Despite European Commission ambitions, many major freight corridors are already saturated, and station lengths remain incompatible with longer formations. "One cannot expand the house by starting with the chimney," a Czech report notes critically, pointing out that DAC deployment lacks the groundwork—a metaphor for systemic underplanning.
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Moreover, compatibility issues with hybrid couplers on locomotives, questions over brake system upgrades (notably the absence of EP brake integration in the basic DAC package), and uncertainty around electrical systems (110V vs 400V) complicate matters further.
Pilot Projects and Pioneers: A Work in Progress
The EU has launched a series of "pioneer trains" to test DAC in real-world conditions. These include approximately 100 trains across Europe, consisting of 20-wagon sets and associated locomotives. Yet even here, expectations appear inflated. Field trials like Green Cargo’s "Steel Shuttle" in Sweden do showcase potential. Trains hauling up to 3,800 tonnes over 1,000 kilometres through harsh winter conditions present a valid testbed—but these focus mainly on mechanical coupling, leaving electrical and data functions largely untested.
The lack of dynamic yard testing, where DAC systems would face daily operational stresses like braking and decoupling at low speeds (1–12 km/h), also raises questions. "Rolling between A and B is not the same as coupling on a hump," as critics put it.
Financial Viability and Risk of Underperformance
Beyond the physical hardware, financial and organisational hurdles dominate the discourse. In Germany, for example, the majority of operators interviewed in a federal survey pointed out that DAC is unworkable without substantial subsidies—not only for equipment but also for personnel training, infrastructure updates, and vehicle certification processes. Even the German federal report concedes that for the first ten years, DAC’s cost–benefit ratio will remain negative, with potential returns only emerging by 2040. This timeline clashes with the EU’s 2030 targets, threatening the credibility of the transition strategy.
Moreover, the standardisation process is lagging. While interoperability is key to DAC’s success, each manufacturer currently proposes its own proprietary solutions, potentially forcing rail operators to maintain up to four variants of DAC components, which severely undermines cost control and repair logistics.
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Ageing Fleet, Unrealistic Assumptions?
Another overlooked issue is fleet composition. Much of Europe’s freight rolling stock is 30–40 years old, with limited remaining lifespan. Retrofitting these with expensive DAC systems may be economically irrational, yet documents from EDDP suggest plans to equip all operational vehicles, even those approaching retirement.
"Are we really investing €40,000 per wagon that will retire in five years?" some industry voices ask. Germany alone faces the paradox of retrofitting 2,400 locomotives aged over 40 years, raising serious questions about return on investment and environmental logic, particularly in light of climate neutrality goals.
While freight wagons may physically last 40–50 years, their digital components likely will not. The German study notes a 12-year lifespan for most electronic and data systems, implying that digital retrofits may require three to four full replacements during the vehicle’s service life. These recurring costs are not fully factored into EDDP’s forecasts, deepening concern about DAC’s long-term sustainability.
According to a study by SCI Verkehr for DB Cargo, DAC could increase rail freight output by up to 15% by 2040. However, this falls well short of the EU’s objective of quadrupling rail freight by mid-century. "To achieve a 400% increase, we’d need more than technology—we’d need a fundamental transformation of infrastructure, policy, and logistics culture," a Czech commentator warns.
Where Do We Go From Here?
Despite its promise, DAC remains a work in progress. While its benefits in safety, automation, and network integration are tangible, questions about cost, feasibility, and timing loom large. Key requirements moving forward include clear, enforceable EU-wide standards, transparent cost models and realistic return-on-investment calculations, targeted funding, including scrappage subsidies for non-viable rolling stock. infrastructure adaptation planning, and coordination with ETCS and other digitalisation projects. The next few years will be critical in determining whether DAC evolves into a cornerstone of Europe’s rail strategy—or a cautionary tale of ambition outpacing reality.
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Source: RAILTARGET; SCI; RAILMARKET