In the history of freight cars, screw couplings have been used exclusively ever since. In this process, a shackle weighing approx. 20 kg has to be placed on the hooks of two wagons so that the two wagons can then be connected to each other by turning a screw thread of the couplings. The air lines for brakes as well as power and data bus lines are then coupled by hand. Thanks to the DAK, freight cars are now automatically connected to each other without the need for manual work by the shunting personnel. At the same time, all the necessary connections are also coupled together.

By 2030, all trains in Europe are to be equipped with a DAK. This is the demand of a joint charter of industry players. The goal of the charter: By 2030 at the latest, freight cars throughout Europe should be able to couple automatically, freight trains should be completely digitized and digitally networked from locomotive to last car.
The industry believes that Digital Automatic Coupling is the most important component of an automation and digitization of rail freight transport. The DAK is intended to create faster and more efficient processes. To achieve this, the charter presents three core demands:

  • Accelerate development phase
    The development phase is already underway and is being driven by a variety of projects from stakeholders in the sector. The signatories of the charter call for greater political commitment to further accelerate the development phase and thus quickly move into widespread implementation.
  • Securing funding for a Europe-wide rollout
    Across Europe, around 450,000 freight cars will have to be retrofitted and equipped with the new coupler technology. It is not only the scale of this task that poses a challenge to the industry, but also the associated costs of up to ten billion euros that will be incurred by the sector. Support programs to finance DAK investments are therefore called for.
  • Establish a European roadmap for DAK migration
    To successfully introduce DAK, clear political guidelines and the creation of framework conditions for the migration process are needed. Timeframes for implementation and specifications for technical standards are needed. To ensure that the nationwide introduction of the DAK is successful, a clear changeover date is required.


For a DAK, a distinction can be made between 5 levels. Stage 0 would be the current screw coupling. From stage 3, however, it is only possible to speak of a functioning automatic coupling, as this is the first time that a power line is also coupled. A level 4 DAK, which is to be introduced in Europe, can couple the air, power and data bus lines in addition to the actual coupling of the cars, has an electropneumatic brake (ep brake) and can uncouple partially automatically.

Level 4 DAKs are equipped with a number of sensors and, thanks to the data lines, important data on the condition of the freight cars can be sent to the locomotive driver. The data line is also an important prerequisite for automatic brake testing, which can speed up train dispatching by up to 45 minutes. Together with automatic shunting locomotives, a freight train can thus be ready to depart almost as quickly as a truck.

Another advantage of the DAK is the ability to provide longer freight trains. This is because today the length is limited by the train hook limit load. The DAK is designed for a greater train hook load and, together with an ep brake, enables significantly longer trains of more than 1km, which means that train capacity can thus be significantly increased.

According to Christian Kuhn, consultant of DACcelerate, a migration of the new DAK is possible in two steps. Starting with the replacement of the spring set including the suspension in the underframe of a wagon, the second step can be the dismantling of the buffers and draw hooks and subsequent installation of the new coupler heads. This is expected to take about 2 hours.

However, in addition to the wagons, the locomotives would have to be converted in a first step. Here, the first step is to use a type of hybrid coupler that incorporates both the new and the old technology. In addition to the actual coupler, 48V converters and a power and data management system are also needed.

Another problem area is mixed operation. Currently, around 350,000 to 450,000 wagons would have to be retrofitted. To enable this conversion in a relatively short time window, so-called wagon pairs would have to be formed. A new DAK is installed on one side of the car and a screw coupling on the other.

The technology behind the data transfer is currently still open. The following three solutions are under discussion:

  • Own data line in the DAK,
  • transmission of the data via the power line (Powerline Communication)
  • Transmission of data via the short radio distance.


Pilot transports with the DAK are to take place from 2023!

The commissioned expert of the contract research project “DAK-Demonstrator”, with a duration of 2.5 years until the end of 2022, assumes that a DAK type has to be selected and the technical and operational functionality has to be proven by 2023. Pilot transports in real operation are then to be carried out from 2023. The further timetable envisages that at European level, within the framework of Shift2Rail, the migration of a DAK will then be completed by 2030.

High costs are associated with the introduction of the DAK. Due to the EU-wide networking of rail freight traffic, the German government considers a conversion to be sensible only in a pan-European context. According to the submission, the German government is currently assuming total costs for the Europe-wide migration of the DAK of 6.4 to 8.6 billion euros (source:


Six European partners form consortium – launch of Digital Automatic Coupling test program

Digital Automatic Coupling for Europe (DAC4EU) is the European consortium that manages the demonstration, testing and approval of DAK for rail freight in Europe. Six companies from Germany, Austria, Switzerland and France have been awarded the contract for the research project “DAK Demonstrator for Rail Freight Transport” by the German Federal Ministry of Transport and Digital Infrastructure (BMVI). Members of the DAC4EU consortium are Deutsche Bahn and its subsidiary DB Cargo, the Swiss and Austrian freight railroads SBB Cargo and Rail Cargo Austria, and the wagon keepers Ermewa, GATX Rail Europe and VTG. The research project is funded by the BMVI with around EUR 13 million and will run from June 2020 to December 2022. The aim of the pilot project is to prepare the selection of a coupler design for Europe-wide introduction.