There are six defined levels of autonomy for autonomous vehicles that are generally accepted as standard definitions for the technology. The levels were originally defined by the Society of Automotive Engineers (SAE) in 2014 in a report aimed towards beginning dialogue on technological definitions of autonomy. The report began with six tiers. Once the National Highway Traffic Safety Administration (NHTSA) adopted the SAE standard in 2016, the six levels of autonomy became the standard across the automotive landscape.
The adoption of the standard quickly turned into its use as a definition of where any given vehicle technology fits within the six levels when the discussion turned to autonomy. Most automakers and equipment manufacturers are now using the six levels globally. The levels are defined as:
Level 0: No automation at all. Most vehicles, including those using standard cruise control and even those with advanced safety equipment such as automatic emergency braking are still considered Level 0 (“Zero”) in terms of automation.
Level 1: Driver Assistance. This level includes most of the simpler driver assistance options like adaptive cruise control, semi-automated parking assistance, etc. The definition specifically states that the vehicle is not in charge of steering and acceleration/braking at the same time. If so, it would become a Level 2 car.
Level 2: Partial Automation. This level allows the driver to take hands off the wheel as the vehicle takes limited control of the vehicle in specific situations. The scenario(s) in which the semi-automated Level 2 vehicle can operate on its own are fairly limited and are usually confined to highway or freeway commuting and the like. Tesla’s AutoPilot and Nissan’s ProPilot Assist fit into this category.
Level 3: Conditional Automation. In this level, the abilities of a Level 2 vehicle are elevated to work under even more conditions. The car can do simple maneuvers such as changing lanes and respond to some dynamic conditions on the road without human intervention. The driver is still considered primary backup, however, and must be ready to retake control at all times. It’s believed that most makers will skip this level due to shady areas of liability and move directly from Level 2 to Level 4.
Level 4: High Automation. At Level 4, the vehicle can control itself nearly all of the time without human intervention. It will only ask for human assistance rarely and then only when it cannot figure out what it’s encountered. It will park itself quickly and safely if no intervention can be had fast enough or if it doesn’t know what else to do. Most of the test vehicles seen on the road for self-driving are at this level of automation.
Level 5: Full Automation. At this point, the vehicle is as good a driver as any human can be and able to make flash decisions and get to most any destination without human intervention. The cars at this level will likely not have manual driving options at all, being sans steering wheel and pedals. These vehicles are not yet available or even in the deepest of Skunk Works trials yet, as most of the work to be done to make them happen is in artificial intelligence.
The full SAE definitions of autonomous driving levels can be found at this link.
Aaron is an automotive journalist living in Wyoming, USA. His background includes technology, mechanics, commercial vehicles, and new vehicle evaluations. Aaron is a member of several automotive media groups and writes for many well-known publications.