Dynamic train unit coupling and decoupling at cruising speed: Systematic classification, operational potentials, and research agenda

The possibility to couple train units into consists, which can be vehicles or platoons, has been proposed to improve, among other, average passenger speed, energy efficiency, and railway infrastructure capacity utilization. We systematically review and categorize the technologies and application of coupling train units into vehicles or platoons, identifying different generations of train coupling, which are used for railway operations. The requirements, compatibility in terms of infrastructure and vehicle equipment as well as backward compatibility are analyzed. The potential of a dynamic train unit coupling and decoupling at cruising speed is proposed, and identified as the 4th generation of train coupling. The possibility of current technology to implement a mechanical dynamic coupling and decoupling at cruising speed is reviewed, with functional requirements and steps of such a process. Based on dynamic coupling at cruising speed, various operating concepts are presented, with focus on commuter-networks between polycentric agglomerations. The potential of dynamic coupling and decoupling at cruising speed might reach travel time reductions in the order of 1/3 and no transfers, for a typical test case in Switzerland between Bern and Zurich.