MITHOS project aims to transform multimodal transport infrastructure management through an innovative AI-driven Decision Support System (DSS). Multimodal transport is crucial to advance safer, more resilient and sustainable mobility solutions for both passengers and freight. However, currently the sector faces significant challenges, including inefficient interconnections between transport modes, high operational costs, and fragmented data management. Existing tools often focus narrowly on specific modes with lack of integration, leading to suboptimal decision-making processes and they do not fulfil with FAIR principles on their data management processes. MITHOS addresses these mayor issues by developing a comprehensive and cloud-based platform that centralizes diverse data sources into a unified and intelligent Federated Smart Data (FSD) module, allowing real-time data collection and integration, which is connected to an AI-based DSS for multi-criteria optimization with an interactive HMI visualization. MITHOS framework includes a Bundle of Fundamental Tools (BFT) for enhanced simulation on multimodal infrastructure assessment and as well as to an Impact Assessment module/SAAS for evaluating the overall benefits and compliance of MITHOS´ proposed measures. MITHOS will be implemented in 4 diverse pilot sites: Bilbao, Hamburg, Vienna/Linz, and Thessaloniki in order to validate its effectiveness across different multimodal contexts/coexistence and infrastructure types. By involving real end-users in the development of this project, MITHOS aims to become the future leading global multimodal traffic infrastructure management platform, promoting safer, more efficient and sustainable transport both inside (first) and outside (second) Europe.