German rail operator Deutsche Bahn said on Friday it has now established exactly what happened after a fault in the digital radio system brought train services across the country to a standstill earlier in the week.
According to the state-owned company, the cause was the scheduled replacement of a so-called switch, a network distribution component. A software error occurred as a result of the replacement.
However, this did not trigger an automatic error message as intended, which is why the affected system did not switch over to a parallel system, Deutsche Bahn said. Instead, the switch had to be carried out manually.
Before doing so, however, staff had to rule out the possibility that it was a cyberattack. Only then could the switch be carried out.
Thousands of passengers were left stranded across Germany for about two hours due to the failure of the GSM-R digital radio system on Tuesday evening.
At around 0:30 am on Wednesday (2230 GMT Tuesday), the radio system was working again and trains were able to continue running.
No further component replacements for time being
According to the railway operator, several measures have been taken to ensure that this incident - which has so far been a one-off - does not recur. For the time being, no further components are to be replaced until the fault has been rectified in collaboration with the device's manufacturer.
In future, maintenance work on the system will also only be carried out at night between midnight and 4 am, and only on the part of the system that is not currently in use.
"One thing is clear: the modernization of our infrastructure is the only way forward," said Philipp Nagl, chief executive of the railway infrastructure company DB InfraGo. "As part of our digitalization strategy, we are therefore currently carrying out another comprehensive overhaul of the existing GSM-R network, upgrading it and making it more resilient."
Radio system to remain in use for at least 10 years more
The Global System for Mobile Communications - Railway (GSM-R) radio system is more than 20 years old, but remains the Europe-wide standard for all railways.
According to Deutsche Bahn, the successor system, Future Railway Mobile Communication System (FRMCS), will not be ready for use for at least 10 years. Until then, the old system must continue to function.
According to the information provided, the railway radio system in Germany is designed with redundancy. If one system fails, the radio initially switches to a twin system. If there are problems there too, the radio switches to a fallback system via the public mobile network.
Deutsche Bahn emphasizes that these additional systems functioned perfectly during the overnight period leading up to Tuesday. However, the automatic switchover did not work due to the lack of an error message.
The incident triggered criticism from politicians and industry associations, which was directed primarily at Deutsche Bahn's outdated infrastructure.
