This paper develops a multilayer network framework for modeling substitution and complementarity effects in multimodal transport systems, with application to inland waterways supported by River Information Services. A utility-based modal choice model combined with cross-elasticity analysis is integrated into a multilayer graph structure.

Using a simulated dataset calibrated for the Lower Danube corridor, results show that substitution effects occur under infrastructure or environmental stress, while complementarity dominates in integrated systems enhanced by real-time information platforms. The study demonstrates that digital layers significantly improve network resilience, efficiency, and multimodal coordination.