Inspection of the radio remote control system of the Zugspitze railway
The train leading up Germany's highest mountain, Zugspitze, has a new locomotive which is controlled remotely by the train driver using a radio remote control. To ensure the locomotive operates reliably and safely, Walter Heydt, rail expert at TÜV SÜD Rail, inspected the safety-relevant and non-safety-relevant features of the 'LocControl 100' radio remote-control system made by Schweizer Electronic AG. The system is used to control the locomotive when the train travels up the mountain, as the locomotive is always on the end of the train facing the valley.
The Bayerische Zugspitzbahn railway has transported tourists and materials up and down Germany's highest mountain from Garmisch-Partenkirchen since 1929. From March 2017 onwards it will do so with a new rack-and-pinion locomotive.
The new locomotive – made by Stadler Rail AG, located in Bussnang, Switzerland – was transported to Garmisch-Partenkirchen and lifted onto the tracks at the end of last year. From Grainau, the rack-and-pinion section overcomes an elevation of 1,880 meters over a distance of 11.5 kilometres and a maximum gradient of up to 25 %. On the uphill run, the locomotive pushes up to 40 tonnes up the mountain. The Train driver is in a cabin at the front of the train, using the radio-control system to control the locomotive, which is always at the end of the train facing the valley. The radio remote control sender or ‘beltpack’, which the train driver hangs in front of his chest in a special harness, is jokingly dubbed ‘the candy-seller tray’ by Walter Heydt, authorised expert at TÜV SÜD Rail.
Walter Heydt inspected and tested the safety-relevant and non-safety-relevant functions of the 'LocControl 100' radio remote control system from Schweizer Electronic AG, Reiden (CH). The assessment first checks that all formal requirements are fulfilled. Once this has been established, compliance with the technical requirements is verified on site, starting with correct installation of the radio remote control system. Both the functions and the radio receiver's connection (interface) to the locomotive control system differ in almost every vehicle type. Given this, the implemented functions and the interactions between the radio remote control system and the locomotive control system must be assessed separately for each type of vehicle. This particularly also includes assessment of the switchover from manual operation to radio operation and vice versa. A special switchover procedure prevents accidental switching. This mainly ensures that the vehicle cannot be set in motion accidentally or unintentionally.
Safety-relevant functions primarily include the control of the brakes. As part of the assessment, the expert simulated faults such as a loose wire at the interface. If the radio connection is interrupted, the vehicle must not simply continue in motion, but must be brought to a standstill within a short tolerance period. Without a signal from the sender of the radio control system, the brakes are always applied. 'An active control signal is needed to release the brakes', explains the expert. To be on the safe side, the new rack-and-pinion locomotive even has two redundant braking systems that are actuated by two different signals. “Even if the radio receiver interrupts just one of those signals, the locomotive's remote control system must immediately apply the emergency brake.“
In the early days of the Zugspitzbahn, the train driver stood in the locomotive facing the valley and received bell signals from another operator at the front of the train. Today, the train drivers are in the cabin facing the mountain, and control the train from there using their portable radio remote control System.
If radio remote control systems are used on shunting locomotives on the public railwayl network, they are subject to approval by the German Federal Railway Authority (Eisenbahn-Bundesamt, EBA). The Federal Railway Authority (EBA) generally uses external experts, who must pass a special authorisation procedure. Walter Heydt successfully passed this procedure and is thus often involved in EBA approvals.