The DAC test marathon

To ensure that it can meet the high standards of rail freight and continue to perform reliably for decades, the DAC is subjected to a rigorous testing programme. And this is by no means a recent development.

Five years ago, early prototypes underwent an extensive programme of more than 2,000 individual trials and 200 climate-chamber tests as part of the DAC4EU project. This work is now continuing under the European EU-Rail FP5 research and innovation programme, specifically through FP5-DACtiVate, a project complementing FP5-TRANS4M-R.

The findings from all the tests carried out so far have resulted in the strongest and most robust version of the DAC to date. At least, that is, until the next round of testing reveals another detail or two that could still be improved.

Testing gets under way again 

Since mid-2025, the test teams working on this forward-looking European project have once again had their hands full. Valerie Baumgartner, who coordinates testing at the Rail Cargo Group, talks us through three major test programmes conducted under FP5-DACtiVate. These have already provided, and will continue to provide valuable insights for the next stages in the development of the DAC.

Test series 1: Climate chamber (August–October 2025) 

Even before ÖBB’s DAC demo train underwent winter trials in the Pongau region of Salzburg, the coupling had already been put thoroughly through its paces in the climate chamber in Minden, north of Bielefeld.

The Minden climate chamber resembles an enormous railway shed, with enough track space to accommodate two freight wagons end to end. A locomotive shunts the wagons into the chamber and leaves them there. The doors are then closed and the temperature inside is lowered to as little as –25°C. It takes around ten to twelve hours before the first test can begin, as enough ice must first form to reproduce the conditions of a truly cold winter’s day.

“There are two basic test scenarios. The DACs must couple reliably at very low temperatures, but they must also be able to uncouple. We test equipment from all the manufacturers at a range of temperatures and in powder snow, very wet snow, ice and other harsh conditions - even in heat of up to +40°C,” Valerie explains, outlining the scope and set-up of the tests.

The climate chamber in Minden was already being used for icy DAC trials in 2021.

Alongside extreme temperatures, absolute precision and consistency in the way the tests are carried out are essential. “We test a huge number of different configurations, and we never carry out a trial just once, as the result could simply be a fluke. We repeat each trial three to five times to make sure the findings are genuinely reliable.”

The testing is broad as well as detailed. The different manufacturers’ DACs are not only tested individually; they are also coupled and uncoupled in a wide range of mixed combinations. Under the strict test plan, all these combinations must be tested with every specified type of snow and at every specified temperature.

“Ultimately, we carry out hundreds of tests. Each one requires not only careful preparation, but also subsequent evaluation and documentation,” Valerie says, summing up the scale of the work involved.

Test series 2: Derailment tests and pushing trials (June–July 2025) 

Safety is paramount in rail freight. This is particularly true of the DAC, as shunting staff will no longer have to step between the wagons. The DAC is also intended to make the train as a whole safer.

To meet these demanding expectations, the DAC is pushed to its limits - and sometimes beyond them - during derailment tests in Görlitz. These tests, also known as pushing trials, are among the most challenging of all.

This is hardly surprising. As a centre-buffer coupler, the DAC carries all the train’s tensile and compressive forces through a much more concentrated load path than a conventional screw coupling.

Put simply, all the forces act through a single point with the DAC. With a screw coupling, they are divided: the tensile forces are transmitted through the coupling in the centre, while compressive forces are absorbed by the side buffers.

Valerie explains the target in more detail: “We do not merely want the DAC to match the performance of the screw coupling. We want it to be twice as good. Instead of the previous 240 kilonewtons, the DAC should be capable of withstanding forces of up to 550 kilonewtons.”

The sheer scale of these forces became clear during the trials in Görlitz. The train had to negotiate an S-curve on the test track while being subjected to extreme loads.

This is a scenario that can also arise in everyday operations - for example during industrial shunting or when locomotives are used to bank a train over a mountain pass. The Semmering is a case in point.

“We pushed the train into the S-curve using three locomotives to generate a force of 550 kilonewtons. A train is particularly unstable when it is being pushed. On routes with numerous curves, this can cause a wagon to derail, especially if it is empty.”

Nearly 100 tests were carried out in Görlitz and approved under the close scrutiny of TÜV SÜD. The condition of the track itself demonstrated the immense forces involved.“ After two weeks of intensive testing, the track had to be replaced because it had been subjected to such severe loads,” Valerie says, describing the extent of the wear. 

Test series 3: Crash tests (Autumn 2026)

The demanding standards that the DAC must meet will also be evident in a forthcoming series of tests. During the crash tests, which are also planned for Görlitz, another extreme scenario will be used to assess the robustness of the DAC.

Valerie, what exactly will you be looking at? If a wagon is not properly secured, it can break free, begin to roll and collide with another vehicle. We want to understand what that does to both the DAC and the wagons at impact speeds of between five and ten metres per second,” she explains.

The test scenario simulates hazardous-goods wagons striking an immovable obstacle, such as a buffer stop. These wagons may carry chemicals that require particularly high levels of protection.

For this reason, hazardous-goods wagons are fitted as standard with AX spring packs, which are especially effective at absorbing impacts and provide an additional level of safety. What do you hope to learn from the tests?

“It is a little like a car crash test. The car may be badly damaged after the impact, but ideally the crash-test dummies remain unharmed. The difference in our case is that the ‘dummies’ are the hazardous goods or chemicals - and naturally, we want to protect them as effectively as possible,” Valerie says, summing up the purpose of the tests.

Of the three test series presented here, the crash tests are likely to push the DAC and the wagons closest to their absolute limits. Whether they prove as successful as the earlier climate-chamber and derailment trials will become clear towards the end of 2026. Based on the experience gained so far, the prospects look good.

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the Europe’s Rail Joint Undertaking. Neither the European Union nor the granting authority can be held responsible for them. 

The FP5-TRANS4M-R and FP5-DACtiVate projects are supported by the Europe’s Rail Joint Undertaking and its members.