As railways are viewed as key to sustainable mobility, the increase of rail’s modal share for both passenger and freight transport will cause congestion problems on many national and urban networks. Virtual Coupling promises to be a game-changer technology for accommodating more trains and increasing service flexibility. Nevertheless, gaps in technological knowhow and regulations are slowing down its adoption.
Virtual coupling is a next-generation signalling concept that, as the name implies, aims at “virtually” coupling trains together when they travel on the same route. This means that distance between trains would shift from an absolute braking distance to a relative safety distance as in cars, allowing them to travel at much closer proximity and, thus, free up space on the rest of the infrastructure. This allows multiple trains to run in a synchronous way, dynamically adjusting their speed based on the preceding train to maintain the safety margin between the trains and form a convoy. Additional information such as the route allows them to optimally virtually couple or decouple based on their needs, while at the same time improving the capacity performances of the overall section.
Building on moving block
Virtual coupling builds upon ERTMS level 3, known as the “moving” block, which is the evolution of the ERTMS level 1 and 2 signalling and speed control systems that are currently in use. From ERTMS level 3, virtual coupling maintains the GSM-R communication properties with the RBC (Radio Block Centres) for reporting the train position, obtained through fixed balises. It also receives the Movement Authority (MA), which specifies the safe distance a train can travel before reaching a danger point. Furthermore, the TIM (Train Integrity Monitoring) system is required to ensure no train cars detach from the convoy. The EVC (European Vital Computer) is required for automatically computing and supervising the braking curve calculated based on the end of the MA.
In addition to these components, virtual coupling introduces a V2V (Vehicle to Vehicle) communication layer for synchronous movement of trains in the convoy. Automatic Train Operation (ATO) is also essential because of the very short driving reaction times required in Virtual Coupling.