A Messaging Strategy based on ITS-G5 for a Bus Blockage Emergency at a Level Crossing

The Intelligent Transportation System protocol stack (ITS-G5/802.11p) supports traffic efficiency and road safety applications in vehicular environments. This protocol allows the vehicle to send continuous status information about road traffic to nearby vehicles or asynchronous warning notifications when an emergency occurs. The former is established by Cooperative Awareness Message (CAM), while the latter is disseminated as Decentralized Environmental Notification Message (DENM). In this work, communications between connected vehicles are based on ITS-G5 specifications considering a realistic Level Crossing (LC) environment in Bordeaux, France. Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications are adopted to exchange both periodic and urgent notifications. An algorithm that explains the messaging strategy is proposed when an emergency occurs. The Packet Reception Ratio (PRR) and the End-to-End (E2E) delay are used as performance metrics to prove its efficiency and study the latency. We consider the simulation of a bus blockage use case at Level Crossing to validate our algorithm independently of vehicle density and speed variations in the considered urban area. We opt for minimizing the accident rate by relying on ITS-G5 particularities for real-time signaling. The proposed communications order and the given behavior of the connected vehicles in the chosen experimental site define a pilot prototype. The latter will be generalized in future work in other chosen sites to prove the efficiency of our messaging proposal in making both road and rail traffic safer.