Organizations such as the global standards body
SAE International (SAE) have proposed terminology to describe technical capabilities. However, most terms have no standard definition and are employed variously by vendors and others. Proposals to adopt aviation automation terminology for cars has also not prevailed. The first consideration is the
operational design domain (ODD). Vendors have taken a variety of approaches to the self-driving problem. Tesla's approach is to allow their "full self-driving" (FSD) system to be used in all ODDs as a Level 2 (hands/on, eyes/on) ADAS. Waymo picked specific ODDs (city streets in Phoenix and San Francisco) for their Level 5 robotaxi service. Mercedes Benz offers Level 3 service in Las Vegas in highway
traffic jams at speeds up to . Mobileye's SuperVision system offers hands-off/eyes-on driving on all road types at speeds up to . GM's hands-free Super Cruise operates on specific roads in specific conditions, stopping or returning control to the driver when ODD changes. In 2024 the company announced plans to expand road coverage from 400,000 miles to . Ford's BlueCruise hands-off system operates on of US divided highways. Names such as AutonoDrive, PilotAssist, "Full-Self Driving" or DrivePilot are used even though the products offer an assortment of features that may not match the names. Despite offering a system dubbed
Full Self-Driving,
Tesla stated that its system did not autonomously handle all driving tasks. In the
United Kingdom, a fully self-driving car is defined as a car so registered, rather than one that supports a specific feature set. The
Association of British Insurers claimed that the usage of the word
autonomous in marketing was dangerous because car ads make motorists think "autonomous" and "autopilot" imply that the driver can rely on the car to control itself, even though they do not.
Concepts The following are useful in understanding the various definitions and criteria in use for self-driving cars.
Driving systems Advanced driver-assistance systems (ADAS) automate specific driving features such as Forward Collision Warning (FCW), Automatic Emergency Braking (AEB), Lane Departure Warning (LDW), Lane Keeping Assistance (LKA) or Blind Spot Warning (BSW). An ADAS requires a human driver to handle tasks that the ADAS does not support. ADAS contrasts to an
automated driving system (ADS), which would be classified by SAE J3016 as Level 3 or higher.
Autonomy versus automation Autonomy implies that an automation system is under the control of the vehicle rather than a driver.
Automation is function-specific, handling issues such as speed control, but leaves broader decision-making to the driver. The European car safety performance assessment programme
Euro NCAP defines "autonomous" as "the system acts independently of the driver to avoid or mitigate the accident". In Europe, the words
automated and
autonomous can be used together. For instance, under Regulation (EU) 2019/2144: • "automated vehicle" means a vehicle that can move without continuous driver supervision, but that driver intervention is still expected or required in the operational design domains (ODD); According to
SAE J3016,
Self-driving The
Union of Concerned Scientists defined self-driving as "cars or trucks in which human drivers are never required to take control to safely operate the vehicle. Also known as autonomous or 'driverless' cars, they combine sensors and software to control, navigate, and drive the vehicle." The British
Automated and Electric Vehicles Act 2018 defines a vehicle as "driving itself" if the vehicle is "not being controlled, and does not need to be monitored, by an individual". Another British government definition stated, "Self-driving vehicles are vehicles that can safely and lawfully drive themselves".
British definitions In
British English, the word "automated" has several meanings, such as in the sentence: "Thatcham also found that the
automated lane keeping systems could only meet two out of the twelve principles required to guarantee safety, going on to say they cannot, therefore, be classed as 'automated driving', preferring 'assisted driving'". The first occurrence of the "automated" word refers to a
UNECE automated system, while the second refers to the British legal definition of an automated vehicle. British law interprets the meaning of "automated vehicle" based on the interpretation section related to a vehicle "driving itself" and an insured vehicle. In November 2023 the British Government introduced the Automated Vehicles Bill. It proposed definitions for related terms: • Self-driving: "A vehicle 'satisfies the self-driving test' if it is designed or adapted with the intention that a feature of the vehicle will allow it to travel autonomously, and it is capable of doing so, by means of that feature, safely and legally." • Autonomy: A vehicle travels "autonomously" if it is controlled by the vehicle, and neither the vehicle nor its surroundings are monitored by a person who can intervene. • Control: control of vehicle motion. • Safe: a vehicle that conforms to an acceptably safe standard. • Legal: a vehicle that offers an acceptably low risk of committing a traffic infraction.
SAE classification is classified as an SAE Level 2 system. In 2014, the association for transport and other industries
SAE International published a six-level classification system – ranging from fully manual to fully automated – as J3016,
Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems; the details are revised occasionally. The system was adopted by the
United Nations Economic Commission for Europe (UNECE) in the form of
UN Regulation No. 157, which came into force in January 2021, and used in over 50 countries. After SAE updated its classification in 2016, (J3016_201609), the US
National Highway Traffic Safety Administration (NHTSA) adopted the SAE standard. The classification is a topic of debate, having been criticized for its technological focus, with various revisions proposed. It has been argued that the structure of the levels suggests that automation increases linearly and that more automation is better, which may not be the case. SAE Levels also do not account for changes that may be required to infrastructure and road user behavior.
Automation levels The SAE classification of Levels is based on the role of the driver, rather than the vehicle's capabilities, although these are related in the form of a "driving mode" (aka driving
scenario). The mode is determined by both an
operational design domain (ODD) and a "dynamic driving requirement." The ODD is the circumstance in which the car is driving, and the driving requirement is what the system must do while remaining safe within the boundaries of that ODD. These two things define the SAE Level. Cars may therefore switch levels according to the driving mode. A human analogy might be a mode in which you can stand unassisted on one leg (the requirement) if you are on the ground (the ODD), but would need support when standing on a
tightrope. Above Level 1, level differences are related to how responsibility for safe movement is divided/shared between the
advanced driver-assistance system (ADAS) and driver, rather than specific driving features (see
Concepts). A car might therefore have Level 3 capability for lane management (the driving requirement) up to 100 km/h (the ODD), but Level 2 at speeds faster than that. Or it might have Level 4 for driverless navigation on designated highways, but Level 2 on urban side roads. ADAS that are considered Level 1 are adaptive
cruise control, emergency
brake assist, automatic emergency brake assist,
lane-keeping, and lane centering. ADAS that are considered Level 2 are: highway assist, autonomous
obstacle avoidance, and autonomous parking. At Level 3 and above, if a car is driving and the ODD changes - for instance, a clear highway becomes a construction zone with hand-signals from a worker - the system must recognize that it is exiting its ODD and fall back accordingly, including asking for driver intervention if necessary. A fully self-driving car would therefore stay at Level 5 for all dynamic driving requirements in all circumstances (speeds, roads, terrains, visibilities, obstacle types, jurisdictions, etc.), while a car with no ADAS controlling the driving requirements would rely on the human driver for that, and stay at Level 0 regardless of the domain.
Mobileye terminology Mobileye CEO
Amnon Shashua and CTO Shai Shalev-Shwartz proposed an alternative taxonomy for autonomous driving systems, claiming that a more consumer-friendly approach was needed. Its categories reflect the amount of driver engagement that is required. Some vehicle makers have informally adopted some of the terminology involved, while not formally committing to it.
Eyes-on/hands-on The first level, hands-on/eyes-on, implies that the driver is fully engaged in operating the vehicle, but is supervised by the system, which intervenes according to the features it supports (e.g., adaptive cruise control, automatic emergency braking). The driver is entirely responsible, with hands on the wheel and eyes on the road.
Eyes-on/hands-off Eyes-on/hands-off allows the driver to let go of the wheel. The system drives, the driver monitors, and remains prepared to resume control as needed.
Eyes-off/hands-off Eyes-off/hands-off means that the driver can stop monitoring the system, leaving the system in full control. Eyes-off requires that no errors be reproducible (not triggered by exotic transitory conditions) or frequent, that speeds are contextually appropriate (e.g., on limited-access roads), and that the system handles typical maneuvers (e.g., getting cut off by another vehicle). The automation level could vary according to the road (e.g., eyes-off on freeways, eyes-on on side streets).
No driver The highest level does not require a human driver in the car: monitoring is done either remotely (telepresence) or not at all.
Safety MRM A critical requirement for the higher two levels is that the vehicle be able to conduct a Minimum Risk Maneuver and stop safely out of traffic without driver intervention. == Technology ==