## 2 State of the Art
### Research Gap and Future Work  
Despite advances in IoV and blockchain implementation, there is a significant gap in research applied specifically to Ro-Ro terminals. Some studies have explored the optimization of storage allocation in Ro-Ro automotive terminals, demonstrating significant improvements in vessel loading efficiency and reduced reliance on storage resources [20; 30; 31]. While some studies have explored the impact of these technologies on general logistics, few have focused on optimizing operations at Spanish Ro-Ro terminals [32]. This gap limits the adoption of advanced technologies in a sector that faces increasing pressure to improve operational efficiency and sustainability. Despite the advances in the implementation of the Internet of Vehicles (IoV) and blockchain in vehicle logistics, significant gaps persist in research, both internationally and in the Spanish context. While these technologies have proven effective in general applications, their specific implementation in port terminals, particularly in Ro-Ro terminals, remains limited. In the international arena, much of the research focuses on the development of IoV and blockchain technologies for vehicle fleets and urban transport networks, leaving aside complex port environments [13]. The available studies usually address land logistics, such as route optimization in intelligent transport systems (ITS), or the use of blockchain for the traceability of goods, but they do not explore in depth how these technologies can be integrated into specific loading and unloading operations at Ro-Ro terminals [33]. Another major gap is the lack of empirical data to support the viability of these technologies in real port environments. Although there are theoretical models and simulations that highlight the potential benefits of IoV and blockchain, few studies have evaluated their impact in terms of operational efficiency, costs, and sustainability in maritime terminals [8]. In addition, interoperability between different IoV and blockchain systems remains a critical challenge, as there are no universal standards that ensure the seamless integration of these technologies into global logistics chains. In the Spanish context, port terminals represent a strategic pillar for the national economy, with ports such as Valencia, Barcelona, Vigo and Santander leading Ro-Ro traffic in EUR. However, the adoption of advanced technologies such as IoV and blockchain in these ports is still nascent. Most Spanish terminals still rely on partially digitized systems and manual processes for vehicular traffic management, leading to operational inefficiencies and higher costs [32]. In addition, how these technologies can be integrated into the specific operations of Spanish Ro-Ro terminals has not been adequately explored. Although there are projects related to port digitalization and automation, such as the National Ports Plan 4.0, academic research on the application of IoV and blockchain in specific terminals is still scarce. This limits the ability of Spanish ports to take full advantage of the advantages of these technologies in terms of efficiency, sustainability, and global competitiveness [34]. Both internationally and in Spain, one of the biggest challenges is the high initial cost of implementing these technologies, which includes the modernization of port infrastructures, the development of IoT networks, and the integration of blockchain systems. In addition, the lack of collaboration between key players, such as port authorities, technology companies, and logistics operators, makes it difficult to implement integrated solutions [1]. Future research can explore the extended application of blockchain in port logistics, particularly in the automation of administrative processes through smart contracts. Additionally, the integration of IoT and IoV with emerging technologies such as 5G and AI could further optimize real-time communication and decision-making in Ro-Ro terminals.