Digital Automatic Coupling:
The backbone for full digital rail freight operations in Europe


The challenge for Europe’s rail freight transport

The automation of freight trains has hardly changed for decades. Employees still need to manually couple trains, walking the length of the train so that each individual wagon can be connected and checked. DB Cargo, Europe’s largest rail freight operator, estimates that its staff carry out the coupling process 54,000 times every day and walk around 700,000 km a year during train formation.

Little progress has been made in the other areas of automation of freight train operations as well. The preparation of a train prior to departure is still a largely manual process. Besides the mechanical coupling of locomotive and freight wagons, brake air hoses need to be connected. The checking of the wagon order, the test of the brakes and the calculation of the train’s braking weight and performance are still done mainly manually. The technical condition of the freight wagons is inspected by operating staff as part of a technical wagon inspection. Finally, even the sign at the end of the train has to be attached manually.

During the train run, the pneumatically controlled brake system limits the possible speed of a freight train. The lack of a safe train integrity functionality makes it impossible to envisage the implementation of European Train Control System (ETCS) Level 3 (moving block) operations in mixed passenger/freight traffic.

It is hard to imagine how, in such an environment of manual interventions and low efficiency, the target of increasing rail freight in Europe by 50% by 2030, as set out in the European Commission’s Sustainable and Smart Mobility Strategy, can be reached without major improvements.

The first step: Digital Automatic Coupler enabled by Shift2Rail

To reach this goal, these inefficient processes clearly need to be changed. The key component as the basis for future freight train automation is the Digital Automatic Coupler (DAC).

DAC decreases the need for manual processes and substantially accelerates train formation processes. As one of the key elements for transforming the European rail freight sector, DAC will (directly or as enabler) increase productivity, efficiency and service quality, leading to an increase of competitiveness. Together with a “smart” increase of capacity, the DAC will be the game changer for shifting more freight traffic to the European rail system, significantly contributing to the European Green Deal, and additionally increasing workers’ safety and value creation for Europe.

The development of the DAC technology has been initiated under the research and innovation activities of the Shift2Rail’s Freight Innovation Programme (IP5). The initial work done by Shift2Rail has lead to an increase in sectorial interest and the creation of the complementary DAC4EU project funded by the German Ministry of Transport and Digital Infrastructure. The project runs from July 2020 to December 2022 and is led by a consortium that includes Deutsche Bahn, Deutsche Bahn Cargo, SBB Cargo, Rail Cargo Austria and freight wagon leasers Ermewa, GATX Rail Europe and VTG.

The outputs coming from Shift2Rail and national initiatives feed into the European DAC Delivery Programme (EDDP) enabled by the Shift2Rail, which in total involves more than 50 entities Europe-wide and is open to new participants , through which the sector will decide on the DAC solution to be implemented across Europe in the coming years. The Shift2Rail Joint Undertaking was instrumental in bringing the partners together and continues to act as an enabler of the programme. The EDDP covers the various aspects necessary for the deployment of DAC in Europe, including a clear target picture for the sector, technological assessments of the available solutions, testing and demonstrations, definition of migration plans, assessing the interfaces with other programmes, business cases, the funding and financing issue, as well as communication and dissemination.

One of EDDP’s main activities focuses on four proposed DAC prototypes going through a testing phase, such as the winter tests carried out by DAC4EU and the Shift2Rail IP5 FR8RAIL IV project. The results from the testing will help determine the best concept. The final decision will be taken by the EDDP based on the results and an evaluation of the life cycle costs.

The challenges the EDDP must overcome to make the transition to DAC happen are substantial. It is estimated that a fleet of around 450,000 to 500,000 wagons will need to be retrofitted over a still to be determined time period. The EDDP is looking into the options to shorten the migration period which would reduce any negative impact on the rail freight sector’s performance in a long period of using both old coupling procedures and DAC.

The target picture: full digital rail freight operations in Europe

The deployment of the DAC would already constitute a game-changing transformation of Europe’s rail freight system. Manual processes in coupling/uncoupling would become uncompetitive as trains equipped with DAC can be longer and heavier and run slightly faster, due to improved longitudinal train forces. New vehicle designs enabled by a central coupler can offer higher payloads.

But the further automation of the other operational procedures during shunting, train preparation and train run is key for boosting the competitiveness of the rail freight sector, offering the replacement of all manual steps and visual inspections – and not just to simplify or to shorten these individual operations.

The further reaching value of a DAC becomes evident when we look at these new functionalities offered for the freight train as a whole. DAC, with energy supplied to all wagons and secure data communication throughout the train, would become the basis for Europe-wide, interoperable, efficient, full digital freight operations, and contribute to a substantial capacity increase on the rail network. This new digital connection between the train’s wagons unlocks the possibility to build-in further digital solutions, and to realise the additional required functionalities and benefits.

The time-consuming manual test of every train’s brakes prior to departure to ensure they are functioning correctly, is usually performed by the driver or vehicle inspector. An automatic braking test device could perform this test and the calculation of the braking capacity, and display the result in the driver’s cab, significantly increasing efficiency. This goes along with an automated wagon registration, delivering a “train setup” (train composition) prior to departure, and actively notifying the operator if it were to deviate from the planned order2.

A digital connection throughout the train especially allows a train integrity function on freight trains. The train integrity test regularly checks whether all freight wagons are still in the train and that no part of the train has become separated. It is therefore the key prerequisite for ETCS Level 3 (moving block) operation in the infrastructure. Accelerated process times, higher train productivity and ETCS Level 3 increase the capacity of the network, which makes the shifting of substantially more transport to rail possible; a matter of highest importance to provide the zero-carbon transport Europe needs to reach its climate objectives. In addition, ETCS Level 3 eliminates the need for expensive axle counters and clear track signalling systems in railway infrastructure.

Electro-pneumatic brakes simultaneously control all vehicles in the train regardless of its length, hence generating lower longitudinal compressive forces in the train, which is not possible with a standard air brake system. Freight trains therefore can benefit from better train dynamics and increased speed, operate in mixed traffic with passenger services and hence achieve shorter transport times. Such a system is also a precondition for running longer trains (up to 1500m train length), a train communication system making the use of distributed power/loco control under all environmental conditions easy. Telematics applications enabled by sufficient energy supply offer multiple options for automating manual tasks with freight wagons/trains and for significantly improved customer information, for example, on the condition of the goods transported.

Automatic uncoupling, controlled by the locomotive and/or remotely from a control centre, generates additional efficiency in shunting processes and especially in marshalling yards. Depending on the final use case definition, this functionality might require an automatic parking brake system on the wagon and a safe remote control technology.

A major benefit for railway undertakings, infrastructure managers and wagon keepers will be achieved by the automation of the technical wagon inspection. On wagon side, sensor-based recording and evaluation technology combined with the aforementioned components, such as automated brake tests, are one element. The information transmitted from the freight wagon then needs to be linked to information from trackside systems, such as video-based feature recognition. It offers a wide range of new options, not only for optimising train preparation but also for condition monitoring, predictive maintenance and in-depth data analysis of components. All this will lead to a reorganisation of maintenance procedures as a whole, and ultimately to higher freight wagon availability and reduced costs.

Making the future possible in one European environment

These automation components are partially available today but not yet as stand-alone solutions. For Europe’s rail freight it is essential that technology is functioning in a seamless, integrated, interoperable, well tested and EU-wide authorised way, with the DAC as a backbone for all freight trains. Further work on these components to the highest Technology Readiness Level (TRL) possible is required to achieve the single European technology framework for full digital freight operations, with a well-managed interface and system integration with DAC to become deployable as of 2025/2026.

The most effective framework within which to achieve this, after a successful DAC selection and specification in 2021/2022, will be the upcoming Europe’s Rail Joint Undertaking, the successor programme of Shift2Rail. All further related technology such as, for example, Automated Train Operation (ATO), needs to be harmonised with the DAC digital backbone in such a framework, to ensure full compatibility and a smart migration with a shortest period possible in order to limit the implications for operators. All European stakeholders should seize this unique opportunity to unite forces within this environment and to focus on the development of one single European system for full digital rail freight operations, to finally bring the sector into the 21st century.