Integration of vulnerable road users in cooperative ITS systems

Introduction: This paper describes the development of an architecture for the integration of Vulnerable Road Users (VRUs), i.e. pedestrians, cyclists and powered two-wheelers (PTWs) in Cooperative ITS (C-ITS) systems, and the requirements for VRU devices. Methods: This paper starts with a literature overview on research related to safety applications using communication between vehicle and VRU, and an analysis of the different use cases for C-ITS for VRUs. An architecture is developed, starting from an architecture of C-ITS systems and incorporating the different alternative configuration for VRUs. Starting from the architecture and the use cases, the requirements for VRU devices are defined. Finally, a roadmap regarding C-ITS applications for VRUs is developed. Results: C-ITS technologies allow to communicate with low latency in highly dynamic environments. C-ITS will be integrated in vehicles and can also become available for VRUs, either as an application on a smartphone or as a dedicated device, which can be integrated in the VRU's vehicle. Two levels of use cases can be identified: awareness of the presence of VRUs near potentially dangerous situations, and collision risk warning, based on trajectories of the road users. A roadmap was developed aligned with the roadmap of the automotive industry. Conclusions: Awareness related use cases are relatively close to the market, as they do not put stringent requirements to the (localization) sensors at infrastructure or vehicles. For the collision risk warning use case, the technical requirements for VRU devices towards sensor accuracy and calculation capabilities are challenging. Other challenges are power consumption, context sensitivity, channel congestion, privacy and security of messages. Standardisation of the messages exchanged between VRUs and other road users and infrastructure is a key issue.