The Digital Automatic Coupler (DAC) is one step closer to fully digitising and automating (de)coupling of freight trains. Europe’s Rail published the results of a December 2025 lab-based test, showing that couplers by different manufacturers have no problem working together.
The tests concerned the latest update to the DAC technology, the “Level 5” iteration. It introduces remote-controlled automatic decoupling, in addition to automatic coupling of air pipes, data cables and power cables, as well as electronically controlled pneumatic (ECP) braking.
The challenge is that four companies manufacture their own versions of DAC Level 5 couplers. In real-life operations, these need to work together seamlessly. The December 2025 laboratory tests showed that they can do so in a controlled environment. The couplers by Voith, Knorr-Bremse, Dellner and Wabtec encountered no problems during the various tests conducted.
The tests
In the laboratory, the couplers were tested while lined up straight, but also deliberately misaligned, up to 22 centimetres sideways or 12.5 centimetres up and down.
The release motors were also tested in three ways: one side releasing alone, both sides releasing while the wagons were pressed together (as when brakes are on), and both sides releasing with no pressure. Each had to finish within 3 seconds.
Moreover, the brake air connection was tested for proper sealing, to make sure that there were no leaks. Lastly, the tests checked that the electrical and data connections worked. A network connection had to be established and remain stable every time the couplers joined. All manufacturers’ couplers were fitted with Voith’s electrical connector.
The tests only had one minor hiccup. The remote-controlled decoupling could not be tested with a central control computer, as is the idea for real-life operation. This computer was not available for the tests, so two people pressed the release buttons at the same time by hand during testing. Proper synchronised testing is planned for later.
As a next step, DAC Level 5 can be tested on real wagons, says Europe’s Rail.