Shift²Rail Project “DACcelerate”

Shift²Rail Project “DACcelerate” – Digital Automatic Coupling for rail freight transportation in Europe




In its Sustainable and Smart Mobility Strategy, the European Commission targets an increase of the rail freight transport in Europe by 50% by 2030.

To reach this goal, several technologies and methods will play a significant role: digitalisation and automation of rail freight opera-tions lead to novel solutions with a major impact providing a critical opportunity to shift the freight transport from road to rail.

Digital Automatic Coupling (DAC) is seen as a “game-changer” solution, a feasible and effective way for the transformation to full digital rail freight operations in Europe to deliver on the Green Deal and Digitalisation Package 2022 objectives. The advantages of DAC stretch across the rail freight sector, from railway undertaking (RU) and infrastructure managers (IM), including their staff to wagon keepers (WK), society and environment, ultimately delivering benefits for rail freight customers. DAC makes automation possible, increases coupling efficiency and safety.


Therefore, DACcelerate aims to manage and directly support the European DAC Delivery Pro-gram (EDDP) in close cooperation with all stakeholders, while continuously engaging with ex-perts and policy makers on EU and member state levels. It will provide strategies, methods and guidelines for successful and cost-efficient transition to fully automatized and digitalised rail freight transport. The project tangibly illustrates the required future technology innovation bricks and respectfully updated operational procedures in an early phase of the roll-out and migration process. Hence, DACcelerate establishes and applies a framework allowing identification of bottlenecks, provide a means of crosssectorial communication between stakeholders and develop a consolidated migration plan to tackle the individual challenges, while harmonizing technical approaches and developments. To perform these tasks in an efficient manner, the efforts have been aligned with existing European structures and activities with relevance for the EDDP. This report covers the deliverable 3.2 with final results of DACcelerate Working Package (WP) 3 for a requirements specification for the Digital Automatic Coupler (DAC) incl. the electrical energy and communication system as well as operational rules for DAC-operations. For achieving the objectives, DACcelerate WP3 strongly cooperates with EDDP WP1.


In DACcelerate WP3 a requirements specification for the DAC incl. the electrical energy and communication system as well as operational rules for DAC-operations in rail freight has been developed. For achieving the objectives, DACcelerate WP3 strongly cooperates with EDDP WP1 with 120 experts from 59 companies across 13 European countries.


In collaboration with EDDP WP1 a requirement specification for a DAC (latch type/Scharfenberg type 10) and for a hybrid coupler (for locomotives) has been developed. In this specification requirements for the mechanical and pneumatical part of the DAC and the hybrid coupler have been defined. 88 requirements have been defined for the DAC and 26 requirements for the freight wagons in which the DAC shall be installed. For the hybrid coupler 82 requirements as well as 17 requirements for the locomotives have been defined.


The specifications cover (amongst others) requirements for installation of the DAC in freight wagons and locomotives (installation space), force requirements for the DAC (tensile and compressive forces, fatigue strength), geometrical dimensions of the DAC, requirements for the pneumatic connection in the DAC as well as for the energy absorption system of the DAC, where different categories of draft gears have been defined.
The specification serves as a basis for the on-going works for DAC regulation (ERA) as well as DAC-standardization (CEN).


DACcelerate WP3 has defined framework conditions for the development of an electrical energy system for freight trains. Based on the use cases for the intelligent freight train which have been defined by EDDP, the requirements for the electrical energy system have been consolidated. Major emphasis has been placed on the evaluation of different voltage systems. As a result, a 400 VAC voltage system has been recommended to and approved by EDDP Decision Boards. Based on all preliminary work mentioned above a requirement specification for the electrical energy system for freight wagons and for locomotives has been developed.


The electrical energy system of the train ensures the electrical supply of the electronic com-ponents in the freight train. The energy system is structured within various basic elements, as shown in Figure 1 for a high level overview.


train energy system

High level overview for the energy system



Based on the train configurations developed and agreed in strong cooperation with the EDDP, the energy supply will be based on a continuous train power line (2 wires). The train power line will be connected by the DAC e-coupler. Here we will find a pair of redundant contacts to connect the power line cables of the vehicles. Using this train power line, a train power sup-ply unit inside a locomotive can feed train configurations with up to 50 wagons and a total length of up to 850 m. For longer trains a second locomotive is requested, building a further train power line segment to be fed by a second locomotive. Up to four locomotives are fore-seen in a train. The feeding of the power line will use 400 VAC, 50Hz/60Hz and a maximum power of 3 kW for one segment. The train power supply will be connected to the locomotives internal electrical energy supply and to the driver, offering a human machine interface (HMI) for control and diagnostics. As the 400 VAC need special protections, a touch protection has to be integrated at the endpoints of a train and further safety relevant measures like ground fault protection, overload protection and short circuit protection will be implemented at the locomotive side.


The wagons will directly be connected to the train power line, to take electrical energy needed for the electronic components inside the wagon, by the wagon power supply on each wagon. Here a limited amount of energy (default: 50 W) is taken from the train line and made available inside the wagon at 48 VDC. This is mainly done using a AC/DC converter from 400 VAC to 48 VDC with a limited power consumption. Additionally, there will be a battery as energy buffer in order to cover failures of the train power supply unit in the locomotive or to overcome contact breaks or to make short-term peak power available for special applications. Inside the train power supply and inside the wagon power supply energy management and monitoring functions will be integrated.


DACcelerate WP3 has defined framework conditions for the development of a communication system for freight trains. Based on the use cases for the intelligent freight trains which have been defined by EDDP, the requirements for the communication system have been consolidated. Major emphasis has been placed on the evaluation of different physical layers for the future communication system for freight trains. As a result, two physical layers have been recommended for practical testing: 10BASE-T1L Single Pair Ethernet (IEEE802.3cg) and Powerline-PLUS (plctec AG).


The communication system is responsible to ensure a transparent, safe and secure communi-cation channel for applications distributed in the train. This enables functionalities to exchange information inside the train (internal train communication system). The following Figure 2 gives a basic first overview of the overall architecture of the proposed communication system for a) the Single Pair Ethernet communication and b) the Powerline-PLUS communication.


For both systems we will have a communication node inside the vehicles, offering an interface for applications to communicate. The communication system will have a master node on the leading locomotive, handling up to 100 Wagons and 4 locomotives in the train. For each wagon the communication node determines during the initialization process the direction of the vehicle and the position of the vehicle in the train. Based on this information, an IP based addressing scheme will be used in both systems. Upper layer protocols could therefore (nearly) be the same for both physical layers recommended for practical tests. For both selected systems an integration into IEC 61375 seems to be possible with some modification to be integrated in a next revision.


train communication

Overview about the two communication system approaches – Powerline Plus and Single Pair Ethernet



For the Single Pair Ethernet system, the physical layer is based on an additional 2-wire twisted pair communication cable installed from the DAC ecoupler to the communication node (Freight Ethernet Train Bus Node, F-ETBN). The technology offers a bitrate of up to 10 Mbit/s. Inside the electrical coupler at least two contact points are needed, realized as redundant solution, to connect the vehicles. Inside the F-ETBN, Ethernet switching is integrated to for-ward messages. The single pair Ethernet allows up to 1,000 m to transmit the signal, and therefore a pure passive cablesolution (bypass solution) can be integrated into the node, bridging the communication line in case of a F-ETBN failure.


For the Powerline-PLUS system the physical layer is based on the train power line already in-stalled for the electrical power system. This technology is integrated in the Powerline Train Bus node (F-PTBN). The net bitrate (for applications) of the Powerline-PLUS depends on the amount of F-BTBNs in the system. However, an integrity function is already part of Layer 2 of the Powerline-PLUS. As the power line is limited to 850 m, the locomotives have to implement a routing function between the different segments. The failure of one F-PTBN is directly bridged by the continuous train power line.


In the locomotive the master function for controlling the communication system is installed, linked to the HMI. A more detailed reference system architecture has been defined for the electrical energy and communication system as well.

The electrical energy and communication system will be the technical backbone for future automation functions, and they extend functionalities of today’s freight trains. The realisation of e.g. a train integrity function or an automated brake test, supported by the electrical energy and communication system, require the definition of safety, reliability and availability requirements for those systems. For the derivation of these requirements, a Safety and Security analysis has been developed.


The definition of the future operational DAC processes has been developed in alignment with major railway undertakings. Together with rail freight operators from EDDP operational pro-cesses which will be affected by implementation of a DAC have been identified, like e.g. oper-ations in marshalling yards, in terminals, in customer sidings in wagon repair workshops. Several case studies have been developed comparing today’s process with screw coupling with tomorrow’s process with a DAC. DACcelerate has investigated several scenarios for technical functionalities of the DAC whether operations in above mentioned different situations is feasible or not and has defined the target DAC operational processes.


Additionally, DACcelerate WP6 did investigations to the impact of ETCS L3 enabled by DAC on traffic and operational performances. For this traffic a reliable and secure train integrity signal has to be delivered. This is necessary for integrating future freight trains into the ECTS system and will not be possible without an energy and communication system. The most promising lines across EU corridors, i.e., those ones which are currently affected by a high congestion level, have been identified, with the support of the project partners and stakeholders. Simulations using software tool OpenTrack have been carried out to analyse in detail the quantitative advantages with the introduction of L3 (with respect to L2), with specific focus on head-way. As no detailed data about real sections have been made available at the time, simulations have been performed on a simplified line created for the purpose of the project. Very interesting results showed that around 30% of improvement in terms of headway can be obtained, giving a further argument about the need for Digital Automatic Coupling for rail freight transportation in Europe.



DAC Scharfenberg





In order to achieve the goal of increasing rail freight traffic, various technologies and methods will play an important role. In this context, VIRTUAL VEHICLE contributes with broad know-how from department overlapping topics.
Decades of research in the areas of wheel-rail contact and vehicle dynamics have led to the development of models for fleet and operational optimization, such as smart maintenance and LCC. Another part of the Freight research field is the instrumentation and testing of the latest monitoring and diagnostic systems, for example in the area of load monitoring, together with important industry partners in large international consortia.


DAC enables automation, increases coupling efficiency and safety. The realization of e.g. a train integrity function or an automated brake test, supported by the electrical power and communication system, requires the definition of safety, reliability and availability requirements for these systems. A RAMS analysis was performed to derive these requirements. To develop a suitable method for performing the RAMS analysis, all relevant standards were studied and analyzed by VIRTUAL VEHICLE and a suitable template and approach to the standards was created. VIRTUAL VEHICLE also investigated which safety analyses are suitable for the railroad sector and how they can be applied.




DACcelerate Digital Automatic Coupling for fully digital rail freight transport

The Shift2Rail project DACcelerate aims to directly support the European DAC Delivery Programme (EDDP) in laying the foundation for an effective and cost-efficient DAC roll-out. The goal is the successful and effective implementation of digital automatic coupling (DAC) across Europe by 2030.


DAC is a major innovation for European rail freight and important for other train automation components focusing on harmonized European specification and migration strategies. The introduction of power and data lines via a DAC also enables the necessary automation of train preparation processes such as the registration of wagon orders, the wagons themselves, automatic brake testing or technical inspection. Complex manual processes are fully automated, and a freight train can be made ready to depart in minutes instead of hours.


An area to which VIRTUAL VEHICLE contributes directly, in addition to its rail expertise, is data communication. Among other things, this technology enables freight trains to implement the latest electronically controlled braking systems. This means that speed can be increased and braking distances shortened. DACcelerate will create and apply a framework to identify bottlenecks, provide a means for cross-sector communication among stakeholders, and develop a consolidated migration plan to address each challenge while harmonizing technical approaches and developments. To accomplish these tasks efficiently, efforts will be aligned with existing European structures and activities relevant to the EDDP. The consortium around key stakeholders such as ÖBB and SCNF will be coordinated by VIRTUAL VEHICLE.



This project has received funding from the Shift2Rail Joint Undertaking (JU) under grant agreement No 101046657. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Shift2Rail JU members other than the Union. The content of this article reflects only the authors view – the Shift2Rail Joint Undertaking is not responsible for any use that may be made of the information it contains.