In the X2Rail-3 project of the Shift2Rail Joint Undertaking, a detailed virtual coupling concept is developed and analysed in an extensive theoretical framework. Based on the paradigm shift from absolute to relative braking distance, various operational scenarios and potential hazards are identified. According to these scenarios and the general functional architecture, the project provides a first definition of the system requirements, detailing both the virtual coupling components as well as the interfaces and interactions with external systems. The subsequent analysis shows that virtual coupling can enable multiple performance benefits for railway operation. Beside the significant increase in capacity through shorter headways and reduced coupling times, additional flexibility and robustness are gained with situationally appropriate, dynamic coupling manoeuvres with a free choice of vehicles. Moreover, virtual coupling can contribute to reducing costs and delays by replacing the mechanical coupler. Aiming for technology readiness level 3, the results of the project illustrate that the concept is feasible from a technological and operational point of view, highlighting the most critical implementation parts in sensors, control and communication. A two-stage implementation approach is proposed to facilitate the introduction of virtual coupling. This is based on a minimum-complexity first stage to introduce the core functionalities and a second stage with incremental implementation of additional virtual coupling functionalities to further improve the operation. This stepwise approach is also corroborated by the results of the impact analysis, which shows a reduced impact for the first stage. The impact analysis illustrates that the fundamental principle of the external systems remains untouched and a full rework is not required. This also implies that virtual coupling will not interfere with the progress of the European Train Control System (ETCS) development and deployment. Therefore, the X2Rail-3 virtual coupling concepts provides a feasible, non-disruptive solution for a more efficient railway transport
