WEBINAR: Hybrid C-ITS
The third international C-ITS webinar organised by C-Roads, titled "Hybrid C-ITS", took place on March 11, 2025, bringing together around 170 participants from 30 countries. The webinar provided a comprehensive overview of hybrid C-ITS communication, explaining its principles, practical implementation, and benefits. Experts from across Europe shared insights into message distribution, interoperability, and real-world deployment, with France’s hybrid C-ITS roadmap presented as a best practice example.
Introduction
Introduction The webinar began with a brief introduction by Martin Böhm, Secretary General of the European C-Roads Platform, who provided an overview of C-Roads and its role in harmonising specifications to ensure interoperability of C-ITS across Europe. He explained that hybrid C-ITS integrates both short- and long-range communication, utilizing various media such as vehicles and infrastructure, in line with the European C-ITS Strategy from 2016. The key focus remains on the bi-directional communication link. Martin Böhm emphasized that both communication types rely on standardised C-ITS message formats. He also clarified C-Roads' specific role in hybrid C-ITS, which primarily focuses on the infrastructure side of communication. An essential aspect of hybrid C-ITS is that all C-ITS messages share the same message ID for a given traffic event across different communication channels, ensuring consistency. Additionally, each message includes a security header to guarantee authenticity and trust.
Video: C-ITS WEBINAR: Hybrid C-ITS – C-Roads (Martin Böhm)
Key Presentations and Insights
Alexander Frötscher – Review of C-Roads cross-tests
Alexander Frötscher provided an overview of how C-ITS use cases are defined within C-Roads and how they are tested and validated through cross-tests across Europe. He began by explaining the C-Roads working cycle, which starts with defining the single C-ITS use cases. These are then proposed and harmonised both internally within C-Roads and with partners such as C2C CC. Once finalised, the full C-ITS specification is published and implemented by members before undergoing testing and validation on public roads in different locations in Europe.
He then presented the message distribution chain, detailing how messages travel from the C-ITS central units to mobile C-ITS stations e.g. in vehicles, with message brokers and clients playing a key role. The first full hybrid specification was published in 2021, marking a significant milestone for C-Roads. He also highlighted that cross-tests enable external parties to participate in the complete validation process. Alexander Frötscher concluded his presentation by showcasing the results of the latest Cross-Test, successfully conducted in 2023. One key finding was that IP-based specifications fully support C-ITS message types, and vehicle fleet operators are actively planning the rollout of C-ITS brokers.
Video: C-ITS WEBINAR: Hybrid C-ITS – Review of C-Roads cross-tests (Alexander Frötscher)
Christian Berg Skjetne – Steps to become operative for long-range C-ITS
Christian Berg Skjetne outlined the steps required to become operational for long-range C-ITS. He began by discussing the current state of the ecosystem, highlighting that two aspects are still missing: the standardisation of the C-Roads "C-ITS IP-based Interface Profile" and the alignment of existing specifications and profiles for use in IP-based systems. However, he emphasized that these are not critical roadblocks, as the system already functions effectively. He then provided practical insights into the required components for IP-based C-ITS and demonstrates an example of message distribution to vehicles via MQTT. In conclusion, Christian highlighted that C-ITS can already be implemented in a standardised and specified manner, enabling both short- and long-range communication in a cost-effective way. This approach allows for almost unlimited coverage without the need for expensive physical infrastructure, making it a scalable and efficient solution for the future.
Risto Öörni – IP-based communication profiles
Risto Öörni provided an overview of IP-based communication profiles for C-ITS message exchange over IP-based networks. To facilitate this, C-Roads has defined specific profiles that enable the seamless exchange of information between back-end systems. He explained that the exchange can follow either a centralised or decentralised approach, using peer-to-peer connections or an interchange node to manage communication. The defined profiles include the basic interface, the improved interface, and transport layer security, each serving different purposes. Risto Öörni then delves into the details of these profiles: the basic interface facilitates communication between two C-ITS actors, whereas the improved interface enables message exchange between two interchange nodes.
He concluded his presentation by emphasising that the C-ITS IP-based interface profile is an integral part of the C-Roads profile specifications, ensuring interoperability within the system.
Video: C-ITS WEBINAR: Hybrid C-ITS – IP-based communication profiles (Risto Öörni)
Marie-Christine Esposito – Best Practice implementation
Marie-Christine Esposito provided insights into France’s success story in achieving full hybrid C-ITS communication. This progress was made through a series of EU-funded C-ITS projects, beginning in 2014, including SCOOP, C-Roads France, InterCor, InDiD, and SCALE. The SCALE project is seen as the final stage before full C-ITS deployment, addressing remaining challenges, with hybrid communication being a key focus. Each project contributed step by step by expanding services, use cases, and system architecture. For instance, SCOOP initially focused on ITS-G5 and hybrid architecture, while InterCor introduced logistics and cross-border elements. Finally, SCALE is integrating additional services such as blue light services, urban logistics, and the hybridisation of short- and long-range communication.
A fundamental principle in France’s approach has been ensuring that messages remain consistent across all communication channels – whether via ITS-G5 or cellular networks – by maintaining uniform layers, with particular emphasis on the Geonet layer. Currently, C-ITS deployments in France are fully operational. The work continues within the SCALE project to establish a truly hybrid environment, collaborating closely with service providers to define their role in C-ITS – with cooperation being the guiding principle.
Video: C-ITS WEBINAR: Hybrid C-ITS – Best Practice implementation (Marie-Christine Esposito)
Conclusions
The third international C-ITS webinar, “Hybrid C-ITS,” successfully brought together experts and policymakers to discuss the latest advancements in hybrid communication for cooperative intelligent transport systems. The discussions highlighted the crucial role of interoperability, message standardization, and the ongoing efforts to expand hybrid C-ITS across Europe. With practical insights from cross-tests, long-range communication strategies, and best practice implementations like France’s roadmap, the webinar reinforced the importance of a harmonized approach to ensure the efficient and widespread deployment of hybrid C-ITS.
