The HEADSTART Glossary provides a library of terms related to the project. Many acronyms and phrases are used across many different fields with different uses and meanings so it is important to lay down the terminology and its specific meaning for HEADSTART. It is an ongoing endeavor which will be constantly updated throughout the project’s lifetime.

Key Terms


Any unplanned event that resulted in injury or ill-health of people or damage or loss to property, plant, materials or the environment or a loss of business opportunity.

Accident scenario

It is the scenario investigated during the entire accident analysis including levels of injury severity, as well as the transport modes that represent a higher risk for VRUs. It is described by the type of road users involved in the accident, their motions expressed as ‘accident types’ and further most contextual factors like the course of the road, light conditions, weather conditions and view obstruction.

ADS – Automated Driving System

The hardware and software that are collectively capable of performing the entire DDT on a sustained basis, regardless of whether it is limited to a specific operational design domain (ODD); this term is used specifically to describe a level 3, 4, or 5 driving automation system.


Attempt to destroy, expose, alter, disable, steal or gain unauthorized access to or make unauthorized use of an asset.

Communication (V2X)

The passing of information from a vehicle to any entity that may affect the road user (e.g. vehicle) and vice versa.

Concrete scenario

Parameterised model of the time sequence of scenes (logical scenario) which begins with an initial scene and defined point in time; the behaviour of the main actor (vehicle under test) is not further specified.

Controlled test environment

Setting under which variables external to the vehicle under test are determined.


Criticality is defined for every vehicle independent from the driver. Criticality is defined as temporal and/or spatial proximity to a situation from which an accident is not evitable. Higher criticality results in higher demands on the human and the Automated Driving Function.

Cyber security

Cybersecurity is the protection of connected systems including hardware, software and data from internal and external attacks carried by malicious entities with or without authorization.

DDT – Dynamic Driving Task

All of the real-time operational and tactical functions required to operate a vehicle in on-road traffic, excluding the strategic functions such as trip scheduling and selection of destinations and waypoints, and including without limitation: 1. Lateral vehicle motion control via steering (operational); 2. Longitudinal vehicle motion control via acceleration and deceleration (operational); 3. Monitoring the driving environment via object and event detection, recognition, classification, and response preparation (operational and tactical); 4. Object and event response execution (operational and tactical); 5. Manoeuvre planning (tactical); and 6. Enhancing conspicuity via lighting, signalling and gesturing, etc. (tactical).

Driver takeover

Action by the driver to regain manual control of the vehicle.


The Ego-vehicle is the automated vehicle from whose perspective the traffic situation is viewed. The data recorded by the ego-vehicle through its sensors describes the traffic situation from its perspective relative to its own condition.


Influencing change of state or condition within a scenario.

Functional scenario

A functional scenario is a temporal sequence that describes one of the behaviors of a system during a specific use case, with a nominal scenario and alternative scenarios. It is described in a linguistic way or with a structured language. Functional scenarios are derived from driving functions. They are used to describe the use case at a high level (higher than logical and concrete scenarios).


Physical injury or damage to the health of persons.


Source of potential harm.

Initial condition

State of the environment and vehicle under test at the beginning of a scenario.

Logical scenario

Beginning with an initial scene, a model of the time sequence of scenes whose parameters are defined as ranges; at a defined point in time, the behaviour of the main actor (vehicle under test) is not further specified.


Physical movement of an actor in a scenario.

Minimal risk condition

Condition of a scenario to which a user or an ADS may bring a vehicle after performing the DDT fall back in order to reduce the risk of a crash when a given trip cannot or should not be completed.

Minimum risk manoeuvre

A procedure aimed at reducing risks in traffic, which is automatically performed by the system when the driver does not respond to a transition demand (e.g. by reducing vehicle speed).

Mixed traffic environment

Traffic environment in which AVs are mixed with other non‐equipped traffic participants such as pedestrians, cyclists, powered two‐wheelers, and other driven vehicles.

Near crash

Event requiring a rapid, evasive manoeuvre to avoid a collision.

ODD-Operational Design Domain

The specific conditions under which a given driving automation system or feature thereof is designed to function, including, but not limited to, driving modes.

Other road user

All possible road users from the perspective of the ego-vehicle (the AV) i.e. pedestrians, bicyclists, motorcyclists, vehicles, automated vehicles.


A group of two or more automated cooperative vehicles in line, maintaining a close distance, typically such a distance to reduce fuel consumption by air drag, to increase traffic safety by use of additional ADAS-technology, and to improve traffic throughput because vehicles are driving closer together and take up less space on the road.


The acknowledgment of the spatial position of an asset in time, involving in autonomous vehicles relative positioning (for obstacle avoidance or precise guidance with respect to the road markings) and absolute positioning (for retrieving from the digital map the information needed for the navigation). 


Combination of the probability of occurrence of harm and the severity of that harm. 


This is freedom from unacceptable or absence of unreasonable risk of physical injury or of damage to the health of people, either directly, or indirectly as a result of damage to property or to the environment. 


Abstraction and general description of a temporal and spatial traffic constellation without any specification of the parameters.

Scenario parameter

A scenario parameter is a value used to describe the characteristics of a scenario (e.g. minimum TTC, average speed, minimum distance and trajectory). 


Snapshot that includes the moving and non-moving elements of the traffic environment, the self-representation of all actors and observers and the relations between those elements. 


State of relative freedom from threat or harm caused by deliberate, unwanted, hostile or malicious acts. 

Security incident

Event or events during which the security of an asset, organization or person is, or might be, compromised, either accidentally or deliberately. 


The severity of the accident describes the injuries to the vehicle occupants and other road users and damage to the vehicle (from material damage to fatal accident). 


Set of components or subsystems that relates at least a sensor, a controller and an actuator with one another. Note 1 to entry: the related sensor or actuator can be included in the system, or can be external to the system. 

System takeover

Assumption of driving control by the vehicle. 

Test case

The set of conditions that are applied to test a function or system. 


Potential cause of an unwanted incident, which may result in harm to a system, individual or organization. 

Threat agent

Person or organisation that can pose threats to cyber security.


The procedure whereby an approval authority certifies that a type of vehicle, system, component or separate technical unit satisfies the relevant administrative provisions and technical requirements. 

Unplanned event

A situation which is unknown [in advance], but assumed as very likely to happen, e.g. [road construction, inclement weather, approaching emergency vehicle, missing lane marking, load falling from truck (collision)] and which requires a transition demand. 

Unreasonable risk

Risk judged to be unacceptable in a certain context according to valid societal moral concepts. 

Use case

Specification of a generalized field of application, possibly entailing the following information about the system: one or several scenarios; the functional range; the desired behaviour; and the system boundaries. Note 1 to entry: The use case description typically does not include a detailed list of all relevant scenarios for this use case. Instead a more abstract description of these scenarios is used.


The passing of information from a vehicle to any entity (vehicles, infrastructure, etc.) that may affect the vehicle, and vice versa.


A machine designed to provide conveyance on public streets, roads, and highways.

Vehicle under test (VUT)

Scenario participant whose behaviour is of primary interest.


Weakness that can be exploited by one or more threats.