The six SAE levels of driving automation are detailed in SAE J 3016-2021, a standard that outlines numerous other concepts pertinent to driving automation systems.
Standard Definitions for Driving Automation Systems
It’s always useful to get things right. When approaching any subject, it remains crucial to possess enough information necessary to make enlightened decisions. Unfortunately, people still get things wrong.
For example, self-driving cars, as expected with an emerging technology, are getting a great deal of attention, but the public’s comprehension of their fundamentals is limited.
You’re not really supposed to call them “self-driving cars.” In fact, the terms “driverless cars” and “autonomous vehicles” are inaccurate as well, according to SAE J 3016-2021: Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles.
Instead, SAE J 3016-2021 (which is not a specification and imposes no requirements) recommends using the terms “driving automation” and “driving automation system.” As discussed in the section of this document dedicated entirely to deprecated terms, vernacular like autonomous, driving modes, self-driving, unmanned, or robotic are often used inconsistently and confusingly to characterize driving automation systems and vehicles equipped with them. Since automation is the use of electronic or mechanical devices to replace human labor, it is the appropriate term and its usage can avoid confusion, misunderstanding, and diminished credibility.
In “driving automation system,” you can see that the term “vehicle” has been excluded. In fact, SAE J 3016-2021 recommends against using terms that make vehicles, rather than driving, the object of automation, since doing so can lead to confusion between vehicles that can be operated by a human driver and an automated driving system (ADS).
About SAE J 3016-2021
Most notably, SAE J 3016-2021 sets forth the levels of driving automation, which have come to be known as the SAE Levels. These levels have reached mainstream and official recognition, even being referenced in the US Department of Transportation’s Comprehensive Management Plan for Automated Vehicle Initiatives. To comprehend these levels, it is essential to understand some key terms outlined in the SAE J 3016-2021 document.
These include the dynamic driving task (DDT), or “all the real-time operational and tactile functions required to operate a vehicle in on-road traffic.” Next is operational design domain (ODD), or “the specific conditions under which a given driving automation system or feature thereof is designed to function.” And then there’s the automated driving system (ADS), which encapsulates all the hardware and software collectively capable of performing the entire DDT on a sustained basis.
Driving Automation Levels in SAE J 3016-2021
With these concepts in mind, the six SAE Levels of Driving Automation are as follows:
Level 0 – No Driving Automation
The performance by the driver of the entire DDT. Basically, systems under this level are found in conventional automobiles.
Level 1 – Driver Assistance
A driving automation system characterized by the sustained and ODD-specific execution of either the lateral or the longitudinal vehicle motion control subtask of the DDT. Level 1 does not include the execution of these subtasks simultaneously. It is also expected that the driver performs the remainder of the DDT.
Level 2 – Partial Driving Automation
Similar to Level 1, but characterized by both the lateral and longitudinal vehicle motion control subtasks of the DDT with the expectation that the driver completes the object and event detection and response (OEDR) subtask and supervises the driving automation system.
Level 3 – Conditional Driving Automation
The sustained and ODD-specific performance by an ADS of the entire DDT, with the expectation that the human driver will be ready to respond to a request to intervene when issued by the ADS.
Level 4 – High Driving Automation
Sustained and ODD-specific ADS performance of the entire DDT is carried out without any expectation that a user will respond to a request to intervene.
Level 5 – Full Driving Automation
Sustained and unconditional performance by an ADS of the entire DDT without any expectation that a user will respond to a request to intervene. Please note that this performance, since it has no conditions to function, is not ODD-specific.
Automation Increases by SAE Level
As you can see, the degree of automation in these mutually exclusive levels increases on a gradient as the levels increase, with Level 0 featuring absolutely no automation, and Level 5 practically sharing similarities with the autonomous systems of science fiction. Notably, the levels are bunched into two overarching groups, with the driver performing part or all of the DDT (Levels 0, 1, and 2) and the ADS performing the entire DDT while engaged (Levels 3, 4, and 5).
This information is only a fraction of the content contained in SAE J 3016-2021: Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles. Anyone in need of the document can acquire it from the ANSI Webstore.