On April 30, 2021, SAE International updated its “Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles,” labeled SAE J3016_202104. This updated version cancels and supersedes the June 2018 version, labeled SAE J3016_201806. Its basic framework remains intact with six levels of driving automation, ranging from no driving automation (Level 0) to full driving automation (Level 5).
The April 2021 revision explains in its introduction: “This revision of SAE J3016 was undertaken in close cooperation between the SAE On-Road Automated Driving (ORAD) Committee and ISO TC204/WG14 through a Joint Working Group formed in 2018. This collaboration brought to bear the knowledge and expertise of global experts in driving automation technology and safety. Several new terms and definitions have been added and multiple corrections and clarifications have been made to address frequently misunderstood concepts and improve the utility of the document, especially for non-native English speakers.”
Under the revision, Level 1 and Level 2 are now referred to as “Driver Support Systems,” with Level 3 to Level 5 still labeled as “Automated Driving Systems,” where the driver is not driving the vehicle when automated systems are engaged. The new term for Level 1 and Level 2 systems removes the confusion of previous versions referring to Level 1 systems as automated.
The chart above depicting the six levels remains unchanged since its last update in 2019, but the revision provides clarification, especially for Level 3 and Level 4 systems. Generally, both Level 3 and Level 4 systems only allow autonomous driving if certain conditions are met. With a Level 3 system, the driver is required to retake control of the vehicle at the request of the system, i.e. when there is a malfunction or when conditions required for the system to function are no longer met. However, Level 4 no longer requires the driver to retake control of the vehicle at any time. Therefore, a vehicle with a Level 4 system does not require traditional controls such as a steering wheel or pedals.
The revision also defines two new related terms for human-in-the-loop systems—“remote assistance” and “remote driving.” SAE defines “remote assistance” as guidance and assistance given to an automated system in situations where the system does not know what to do on its own. A person providing remote assistance does not take control of the vehicle but instead simply assists the vehicle system. However, “remote driving” is defined as a situation where a human who is not in the vehicle takes control of the vehicle and does the driving. SAE does not consider this a type of automated driving.
SAE also defines the concept of “failure mitigation strategy” as a vehicle function “designed to automatically bring an [automated driving system] equipped vehicle to a controlled stop” following either a driver’s prolonged failure to retake the controls in a Level 3 system or a system failure or external event that incapacitates the automated driving system.
Implying future changes to the standard, Barbara Wendling, chairperson for the SAE J3016 technical standards committee, said, “As the development of automated driving technologies continues on a global scale, SAE J3016: Levels of Driving Automation has evolved to align with developing technologies and deployment strategies. Our collaborative partnership with ISO allowed us to expand and refine the recommended practice to better equip international customers with clear, concise and consistent language and definitions.”