Eurasian rail transport has made significant strides in recent years, demonstrating its po- tential as a critical player in the global supply chain. Yet, it remains confronted with challenges, particularly in meeting the diverse demands of today’s complex global sup- ply chain. The traditional ’one service for all’ operational strategy needs to address the unique needs of a global supply chain, underscoring the need for more tailored solutions. Further research is required regarding the Scheduled Service Network Design (SSND) in the context of international rail freight networks that consist of multiple rail systems featuring diverse railway gauges. We propose a time-space formulated I-SSND model designed explicitly for a relay international rail freight transport system. This innova- tive model seeks to provide heterogeneous services for shipments with differing origins, destinations, releases, and due times. The initial application of this model in Eurasian rail freight transport has yielded encouraging results, showcasing its potential for broader implementation within international rail freight transport.