The RAIL4EARTH project, carried out under the Europe’s Rail Joint Undertaking (ERJU), focuses on the decarbonization and sustainable development of railway systems. One of its key areas is the development of interoperable and safe hydrogen refueling stations for rail applications. This paper presents the research and development activities conducted within Work Package WP9, including the analysis of technical interfaces (mechanical, electrical, communication, and safety) and ensuring compliance with SAE J2601, while being informed by the SAE J2601/5 Technical Information Report (TIR). The engineering challenges related to the design of hydrogen refueling connectors for trains are discussed, with particular attention to high mass flow rates, material requirements, and operational safety. The final outcome of the R&D work will be the demonstration of a universal refueling interface compliant with European and global standards, enabling the rapid deployment and commercialization of hydrogen technologies in the railway sector.