Message Types

Key V2X Message Types

V2X communication is built on standardized message formats that allow vehicles, infrastructure, and other road users to exchange critical information reliably and efficiently.

These messages are defined primarily by ETSI (European Telecommunications Standards Institute) and SAE (Society of Automotive Engineers) standards.

Below are the most important message types used in current and emerging V2X systems:

Basic Safety Message (BSM) / Cooperative Awareness Message (CAM)

• Purpose: Provide real-time updates about a vehicle’s status to nearby vehicles and infrastructure.
• Contents: Vehicle position (GPS), speed, heading, acceleration, size, and basic status information.
• Use Cases: Collision avoidance, situational awareness, and other Day 1 safety applications.
• Standards:
  • BSM: SAE J2735 (used mainly in North America)
  • CAM: ETSI ITS (used in Europe)

Decentralized Environmental Notification Message (DENM)

• Purpose: Notify nearby road users about specific hazards or events in the driving environment.
• Contents: Incident details such as accidents, roadworks, slippery roads, or the presence of emergency vehicles.
• Use Cases: Warn vehicles about temporary or dynamic hazards that influence driving behavior.
• Standards: ETSI ITS.

Signal Phase and Timing (SPaT)

• Purpose: Communicate real-time traffic signal status and timing information from infrastructure to vehicles.
• Contents: Current traffic light phase (red, yellow, green) and time remaining until the next phase.
• Use Cases: Enable intelligent applications such as Green Light Optimal Speed Advisory (GLOSA) and intersection safety.
• Standards: SAE J2735 and ETSI standards.

Map Data Message (MAP)

• Purpose: Describe detailed intersection geometry and lane configurations.
• Contents: Layout of lanes, connectivity, and associated traffic control data.
• Use Cases: Assist vehicles in understanding complex intersections and executing cooperative maneuvers.
• Standards: SAE J2735.

Cooperative Perception Message (CPM)

• Purpose: Share sensor information or processed data about objects detected by vehicles or infrastructure.
• Contents: Object location, type, and movement data extending perception beyond the direct sensor range.
• Use Cases: Improve situational awareness in occluded areas or blind spots, supporting Day 2 and Day 3 applications.
• Standards: ETSI ITS.

Vulnerable Road User Awareness Message (VAM)

• Purpose: Communicate the position and movement of pedestrians, cyclists, and other vulnerable road users.
• Contents: Location, speed, trajectory, and device identification of VRU participants.
• Use Cases: Enhance pedestrian and cyclist safety by alerting nearby vehicles and infrastructure.
• Standards: ETSI ITS.