Part I: What is Digital Automatic Coupling and what are its levels?

What is DAC and what are its levels?

By 2030, trains all over Europe are to be equipped out with Digital Automatic Coupling (DAC). Since it will take a little while to get there, we’ve answered all the basic questions for you about DAC in the first part of our series:

What is DAC?

Digital Automatic Coupling connects wagons so that they form a train. The special thing about DAC is that this connection, or coupling procedure, is automated. Uncoupling at DAC Level 4 is partially automated and should be in use by 2030. What’s more, DAC Level 4 provides wagons with a continual electricity supply and consistent data connection. This will make it possible in the future for wagons to communicate with each other and with the locomotive. DAC has different levels according to their stage of development. 

What are the levels?

There are up to five different levels for Automatic Coupling. The higher the level, the more features there are. Screw coupling is currently in use (SC in the diagram). DAC comes in from Level 3 upwards, because a power cable gets coupled with it. Several Level 4 prototypes exist right now and are undergoing extensive tests. The goal for the future is to have a Level 5 DAC system where uncoupling is also automated.

Why do we not just go straight to DAC5?

The first concepts for DAC5 are in the early stages of development, while prototypes already exist for DAC4. Further safety aspects also need to be considered for DAC5 that are linked to cybersecurity issues. As the graphic shows however, every DAC4 prototype has to be upward compatible with DAC5. This can be done by integrating a small motor, for example. Moreover, DAC4 is already facilitating more automation and digitisation in rail freight transport. Introducing DAC4 means that solutions for brake tests, the order of wagons and calculating train braking distances can already get underway. The full roll-out of DAC5 will come once the train composition process has been fully automated.

Stay tuned: in the next part, you’ll find out more about all the countries involved in automatic Coupling (AC)!

In the course of the funding project TARO - which is supported by the Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology and the Austrian Research Funding Agency (FFG) - RCG deals with processes to become "DAK ready".