The DAC is a state-of-the-art coupling system for freight cars. It combines mechanical coupling with digital data transmission, enabling the automation of train processes. It is a key component of the Digital Freight Train (DFT), supporting end-to-end power and data connections, automated brake testing, train integrity checks, digital condition monitoring, early fault detection, and automated maintenance scheduling.

The DAC is based on impending European Technical Specifications for Interoperability (TSI), as well as standards defining the requirements for automatic coupling systems, such as EN 18171. The system is being developed by various EU research projects – especially Europe’s Rail FP5-TRANS4M-R – which are drawing up the key requirements and technical principles for standardization bodies.

DACs transmit data to central control systems via integrated electrical interfaces and data lines. Knorr-Bremse’s system uses the FreightControl automation system, which processes information such as brake status, freight car data and diagnostics and delivers it to the loco.

The DAC was developed specifically for the European market: As well as mechanical coupling and decoupling functions, it supports a broad range of digital functions unmatched by older systems that are primarily mechanical in operation and cannot automatically decouple.

DAC types differ in terms of their functionality:

• Type 1: mechanical only
• Type 2: + pneumatic
• Type 3: + electrical
• Type 4: + data transmission
• Type 5: + automatic decoupling + Digital Freight Train automation functions

DAC Type 5 supports full automation of all coupling and decoupling processes and was chosen as the standard for Europe under the Europe’s Rail – FP5-TRANS4M-R program.

Yes, using our retrofit kits, our DAC solutions can be installed in existing freight cars without major technical modifications. FreightLink is the digital automatic coupler for freight cars; HybridLink is our coupling solution for locomotives, combining digital and traditional screw coupling technologies. Thanks to the way freight cars are designed, it is relatively easy to retrofit DACs – a process which the DACFIT project is currently analyzing and preparing across Europe. A total of up to 500,000 freight cars and 15,000 locomotives will need to be upgraded in the EU, so one of our top priorities is ensuring that our systems can be seamlessly integrated.

Following a planned series of test programs and commercial Pioneer Trains in the late 2020s, the EU is aiming for a DAC rollout in the 2030s. Pilot projects are already underway in Germany, Austria, Switzerland and other EU countries. The main projects include DAC4EU, TRANS4M-R, DACtivate, DACFIT, Pioneer Trains and the European DAC Delivery Programme (EDDP). These projects are testing various coupler types, systems integration, operating procedures and certification requirements. The technology should be ready for official approval by 2026.

The rollout is supported by the EU-funded public-private partnership Europe’s Rail Joint Undertaking and associated development projects such as FP5-TRANS4M-R, DACtivate and DACFIT, as well as national programs such as DAC4EU (run by the German Federal Ministry for Transport). Commercial Pioneer Trains are being financed by the Connection Europe Fund. Additional financing models and government incentives will be required to support the multinational rollout.

The Digital Automatic Coupler enhances safety, reduces shunting times, enables the digital networking of freight cars and so improves overall rail freight efficiency. In addition, improved lateral and longitudinal dynamics support longer and faster trains – potentially, trains up to 1,500 meters in length. Thanks to additional train integrity monitoring, it will be easier to integrate faster freight trains into passenger train traffic and thus optimize infrastructure utilization. Automatic coupling and decoupling, digital data communications and faster processes will save time and money – up to 90 minutes can be saved per train just by automating today’s manual coupling and brake testing processes. Electric actuators and digital control systems will reduce manual tasks and accident risks while at the same time enhancing safety and ergonomics. Finally, the DAC will make it easier to monitor each train’s technical condition and status using sensors and diagnostic data. In short, the DAC will help to reduce train preparation times, improve rail network capacity and cut lifecycle costs.

Knorr-Bremse is one of the leading suppliers of DAC technology. Other manufacturers are working with Knorr-Bremse in EU programs to develop interoperable solutions and systems.

To ensure that DAC systems are fully interoperable across Europe’s vast rail network, partners are joining in common technical standards, cross-sectoral collaboration in the EDDP, and EU-wide coordination under Europe’s Rail. The various program partners are working closely together on standardizing the system design and certification process. KnorrBremse has been a member of the European DAC Delivery Programme since its inception and is also a founding member of Europe’s Rail Joint Undertaking. In various working groups, we are contributing to the DAC’s technical specifications and standardization, as well as the formulation of suitable business models. Our ultimate objective is to digitalize Europe’s entire rail system and, in the long term, shift freight transportation from road to rail.