In 2013, the US Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) adopted the levels of autonomy outlined in the SAE International’s standard J3016 (download document) officially. SAE J3016 defines six levels of automation that can be used by policymakers, automakers and suppliers when classifying a vehicle’s autonomous capabilities
The pivotal change occurs between Levels 2 and 3, when responsibility for monitoring the driving environment shifts from the driver to the system.
Level 0 – No Automation
The human driver does everything at level 0 including accelerating, steering, braking, and navigating. This is what most of us are used to.
Level I – Driver Assistance
In some circumstances, the car can either steer or control vehicle speed, but not both simultaneously. The driver is fully responsible for controlling the vehicle and taking over if the assistance system acts inappropriately. Adaptive cruise control is a common technology at level 1.
Level 2 – Partial Automation
In some circumstances, the vehicle is able to steer, stay within a lane, accelerate, decelerate and brake without driver input. Actions such as responding to traffic signals, merging or changing lanes and scanning for problems all continue to be the driver’s responsibility and they must monitor the road at all times. The driver can have their hands off the wheel and foot off the accelerator in some level 2 implementations.
Audi Traffic Jam Assist, Cadillac Super Cruise, Mercedes-Benz Driver Assistance Systems, Tesla Autopilot, Volvo Pilot Assist are examples of current (2018) level 2 technology.
Level 3 – Conditional Automation
Pivotal changes occur in level 3 as responsibility shifts from the driver to the autonomous system. Drivers are still necessary and must be able to take over at any time at this level but in the right conditions, the vehicle actively monitors the entire environment. The system only prompts the driver to intervene when it encounters a scenario it can’t navigate.
Audi Traffic Jam Pilot available in future Audi A8s is level3 autonomy.
Level 4 – High Automation
In certain conditions the vehicle can operate without driver input or oversight. Road type and geographic area determine where the vehicle can operate. Potentially the operator could handle driving duties on most roads and then become a passenger when driving on the highway.
Level 4 vehicles are “designed to perform all safety-critical driving functions and monitor roadway conditions for an entire trip.” Prototypes of this functionality exist, but nothing is close to being available commercially.
Level 5 – Full Automation
The driverless car can operate on any road in any conditions a human driver could negotiate in level 5. A driver need only enter a destination. No examples of this level of autonomy current exist.