Glossary of Terms

A standardized message format used to transmit essential safety-related information between vehicles, infrastructure, and other elements of the transportation ecosystem.

A BSM typically contains data such as:

Vehicle Position: Information about the vehicle's current geographical location, usually specified in terms of latitude and longitude coordinates.

Vehicle Speed: The vehicle's current speed, expressed in meters per second (m/s) or kilometers per hour (km/h).

Vehicle Heading: The direction in which the vehicle is traveling, typically provided as a compass heading or angle relative to true north.

Acceleration: The rate of change of the vehicle's speed over time, indicating whether the vehicle is accelerating, decelerating, or maintaining a constant speed.

Vehicle Size and Type: Descriptors indicating the size, type, and classification of the vehicle, such as passenger car, truck, motorcycle, or emergency vehicle.

Timestamp: The time at which the message was generated, allowing receivers to determine the freshness of the data.

A communication technology that enables vehicles to communicate with other vehicles, infrastructure, and pedestrians.

Vehicles equipped with communication technologies that allow them to exchange information with other vehicles, infrastructure, and the environment.

Measures and technologies designed to protect V2X systems from unauthorized access, data breaches, and malicious attacks, ensuring the integrity, confidentiality, and availability of communication and data.

A specialized analysis and evaluation protocol developed by DENSO to ensure the highest level of product safety by avoiding fire hazards in the product environment.

A communication technology specifically designed for vehicle-to-vehicle and vehicle-to-infrastructure communication in intelligent transportation systems.

Emergency Vehicle Preemption (EVP) is designed to give emergency response vehicles a green light on their approach to a signalized intersection while providing a red light to conflicting approaches.

Freight Signal Priority (FSP) is a traffic signal modification that extends a green light’s timing to allow an approaching truck to make it through an intersection without stopping. The main purpose for giving trucks extra green time is to increase safety by reducing the potential for the truck to run a red light and cause a collision. The secondary purpose is to reduce the delays and congestion that are caused by the longer time it takes trucks to accelerate to the posted speed limit.

Communication from roadside infrastructure, such as traffic lights or road signs, to vehicles, providing important information for navigation and safety.

An advanced application which aims to provide innovative services relating to different modes of transport and traffic management and enable users to be better informed and make safer, more coordinated, and 'smarter' use of transport networks.

A standard developed by the International Organization for Standardization (ISO) titled "Road vehicles – Cybersecurity engineering." This standard provides guidelines and requirements for the cybersecurity of road vehicles, including passenger cars, trucks, buses, and other types of vehicles. ISO 21434 outlines a systematic approach to identifying, assessing, and mitigating cybersecurity risks throughout the vehicle's lifecycle, from design and development to operation and decommissioning. It covers various aspects of vehicle cybersecurity, including risk management, security by design principles, threat analysis, security testing, and incident response. Compliance with ISO 21434 helps ensure that vehicles are resilient against cyber threats and vulnerabilities, thereby enhancing safety, privacy, and trust in connected and autonomous vehicles.

Standardized protocol used to exchange map-related information between vehicles and infrastructure in intelligent transportation systems. MAP messages contain detailed geographic and attribute data about road networks, such as lane configurations, speed limits, traffic signs, intersections, and other relevant features. By sharing MAP data, vehicles can enhance their situational awareness, improve navigation accuracy, and support advanced driving assistance systems (ADAS) and autonomous driving functionalities.

A device installed in a vehicle that facilitates communication between the vehicle and other entities such as other vehicles, infrastructure, pedestrians, and the cloud.

Remote updates of vehicle software and firmware via wireless communication, allowing manufacturers to add new features, improve performance, and address security vulnerabilities.

The Personal Safety Message (PSM) is used to broadcast safety data regarding the kinematic state of various types of Vulnerable Road Users (VRU), such as pedestrians, cyclists, or road workers.

A flat board made of non-conductive material, typically fiberglass, epoxy, or other composite materials, with conductive pathways etched or printed onto its surface. The "PCB" referenced on this website is the internal workings of the Roadside Unit, without the exterior case.

A standard protocol used in V2X (Vehicle-to-Everything) communication, particularly in the domain of V2V (Vehicle-to-Vehicle) and V2I (Vehicle-to-Infrastructure) communication. RTCM messages contain data related to vehicle position, velocity, and other parameters necessary for accurate and reliable navigation and communication. These messages are exchanged between vehicles, infrastructure units, and other components of the transportation system to support applications such as collision avoidance, traffic management, and cooperative driving.

A device installed along roadways or at intersections that facilitates communication between vehicles and the infrastructure.

A SCMS is a centralized system responsible for managing security credentials, including certificates and cryptographic keys, used to secure V2X communication.

The primary functions of an SCMS include:

Certificate Management: Generating, distributing, and revoking security certificates for V2X devices, such as vehicles and roadside units (RSUs), to authenticate their identities.

Key Management: Generating and distributing cryptographic keys used for encryption and decryption of V2X messages, ensuring the confidentiality and integrity of communication.

Security Policy Enforcement: Enforcing security policies and protocols to ensure compliance with established standards and regulations governing V2X communication security.

Trust Establishment: Establishing trust relationships between V2X entities to validate the authenticity of exchanged messages and prevent spoofing or tampering by unauthorized parties.

SCMS plays a crucial role in securing V2X communication, protecting against threats such as malicious attacks, unauthorized access, and data manipulation. It enables trusted and secure interaction between vehicles, infrastructure, and other components of intelligent transportation systems, thereby enhancing safety, efficiency, and reliability on the road.


The message from the Traffic Signal Controller to the RSU. It provides information about the current signal phase (such as green, yellow, or red) and timing at a traffic signal intersection. This data is propagated from the intersection’s traffic signal controller to the roadside unit for transmission to equipped devices using V2X (Vehicle-to-Everything) communication technologies.

A standardized message broadcast by the on-board unit to the roadside unit to request for signal priority or preemption at a traffic light.

A device used to manage the operation of traffic signals at intersections or other locations where traffic flow needs to be regulated. It is typically housed within a traffic signal cabinet located at the intersection.

Used to provide extra green time at intersections to larger and street-running transit vehicles, such as trucks, buses, light rail, and streetcar. By helping the bus or truck avoid a stop at a red light, this additional time can help the bus arrive at stops on-time, and can prevent traffic delays and congestion. It also improves safety by helping these vehicles clear the intersection on a green light when it may be difficult to stop.

A standardized message format used to disseminate real-time traffic and travel-related information to vehicles and travelers. TIM messages contain details such as road closures, construction zones, accidents, weather hazards, and other incidents that may affect traffic flow or safety. By broadcasting TIM messages over V2X communication channels, transportation authorities and infrastructure operators can provide timely updates to drivers and autonomous vehicles, allowing them to make informed decisions about route planning, speed adjustment, and other driving behaviors.

Refers to the ability of electronic components and systems within a vehicle to communicate with each other using the Controller Area Network (CAN) bus protocol. The CAN bus is a standardized communication protocol widely used in automotive applications to enable data exchange between various components, including engine control units (ECUs), sensors, actuators, infotainment systems, and more.

Communication between vehicles and cloud-based platforms, enabling data exchange for services such as navigation, entertainment, and remote diagnostics.

Refers to communication between a vehicle and various entities such as other vehicles, infrastructure, pedestrians, and the cloud.

Communication from vehicles to roadside infrastructure, enabling vehicles to request information about road conditions, traffic signals, and other relevant data.

Communication between vehicles and pedestrians or personal devices carried by pedestrians, enhancing safety by providing alerts to both parties.

Communication between vehicles, enabling them to exchange information such as speed, position, and status to improve safety and traffic efficiency.

Refers to individuals who are at a higher risk of injury or fatality when interacting with motor vehicles on the road due to their lack of protection or visibility. VRUs include pedestrians, cyclists, motorcyclists, and users of non-motorized vehicles such as scooters and skateboards.