Non-Negotiated Implicit ETSI VAM Clustering

Including Vulnerable Road Users (VRUs) such as pedestrians and cyclists in Cooperative Intelligent Transport Systems (C-ITS) is key to improving road safety, but it also increases the number of active communication nodes and, as a result, the channel load. In dense scenarios, this can lead to congestion, increased contention, and reduced reliability in Vehicle-to-Everything (V2X) communications. Clustering has been proposed as a way to address this issue by allowing a single node to represent multiple VRUs. However, the clustering scheme defined by European Telecommunications Standards Institute (ETSI) relies on explicit negotiation and in-cluster communication, which introduces additional signaling and assumes reliable message exchange. In this paper, we propose an implicit clustering mechanism for VRU Awareness Messages (VAMs) that removes the need for explicit coordination between nodes. Instead, clusters emerge directly from regular broadcast messages, without additional negotiation or maintenance signaling, and remain robust even under lossy communication conditions. Simulation results show that the proposed approach reduces channel load by approximately 20% compared to the ETSI clustering scheme while achieving higher VRU awareness levels that are comparable to standalone operation.