Enhancing the Safety of Vulnerable Road Users: Messaging Protocols for V2X Communication

The protection of vulnerable road users (VRUs) by means of V2X communication is increasingly considered for the next generation of cooperative safety systems. Two messaging protocols are being standardized: (i) With collective perception for sensor data sharing: VRUs can be passively perceived by the local sensors in vehicles and roadside units, which disseminate this information in dedicated messages carrying lists with VRU and other objects. (ii) VRUs can actively transmit messages in order to make other road users in their vicinity aware of their presence. This paper carries out a performance evaluation of a scenario with the two main messaging protocols and also their combined deployment, and compares them with two baseline approaches. Simulation results for a representative roundabout scenario with manifold interaction among vehicles and pedestrians indicate that the combination of sensor data sharing and active VRU transmissions performs best: It provides the highest VRU detection rate and the shortest VRU detection latency. This approach keeps the channel busy ratio below a critical threshold, which prevents the data congestion control of the V2X communication system from its activation.