The levels of autonomous driving are defined by SAE International (Society of Automotive Engineers) in a standard known as J3016. These levels, from 0 to 5, describe the increasing degree to which a vehicle’s automation system can perform driving tasks, with the human driver’s role decreasing at each level.

Here is a breakdown of the six levels:

Level 0: No Driving Automation

• Definition: The human driver is in complete control of all driving tasks (steering, braking, accelerating).
• System Role: The vehicle may have systems that provide momentary assistance or warnings, but they do not actively control the vehicle.
• Examples: Systems like automatic emergency braking, blind spot warnings, or lane departure warnings fall under this level, as they are a safety feature that provides a warning or a short, non-sustained intervention.

Level 1: Driver Assistance

• Definition: The vehicle can provide sustained assistance with either steering or speed control, but not both at the same time. The driver must remain fully engaged and is responsible for all other aspects of driving.
• System Role: A single automated system provides assistance.
• Examples: Adaptive Cruise Control (ACC), where the vehicle maintains a set speed and a safe distance from the car in front of it, is a common Level 1 feature. Lane-Keeping Assist (LKA) is another example, as it provides steering input to keep the car centered in its lane.

Level 2: Partial Driving Automation

• Definition: The vehicle can control both steering and speed simultaneously under specific conditions. The driver must remain fully attentive and ready to take control at any moment. This is often referred to as “hands-off” driving, but the driver must still have their “eyes on” the road.
• System Role: The vehicle’s advanced driver-assistance systems (ADAS) manage both the lateral (steering) and longitudinal (acceleration/braking) control.
• Examples: Systems like Tesla’s Autopilot and GM’s Super Cruise are considered Level 2. They can navigate highways, but the driver is still ultimately responsible and must be prepared to intervene when the system disengages or faces a situation it can’t handle.

Level 3: Conditional Driving Automation

• Definition: This is a major leap forward, as the vehicle can handle all aspects of driving, including environmental detection, under certain conditions. The key difference from Level 2 is that the driver does not need to continuously monitor the vehicle. The driver can be “eyes-off” but must be ready to take over when the system issues a takeover request.
• System Role: The automated driving system (ADS) can make decisions and navigate for extended periods. It will alert the driver with sufficient time to resume control if it encounters a situation outside of its operational design domain (ODD), such as bad weather or a complex intersection.
• Examples: Mercedes-Benz’s Drive Pilot is one of the few Level 3 systems available in select countries. It is designed for specific, low-speed traffic jam situations and will alert the driver to take over when the traffic clears.

Level 4: High Driving Automation

• Definition: The vehicle is fully capable of driving itself under certain conditions without any human input. If the system encounters a situation it cannot handle, it will perform a “fallback” maneuver, such as safely pulling over to the side of the road, rather than requiring the driver to take over. The driver is not required to be alert or ready to intervene within the ODD.
• System Role: The ADS handles both the driving task and the “fallback” function.
• Examples: This level is most commonly seen in commercial applications like robotaxi services (e.g., Waymo and Cruise) that operate within a limited, predefined “geofenced” area of a city. These vehicles can handle all driving in that zone, but they are not yet able to operate anywhere in the world.

Level 5: Full Driving Automation

• Definition: The “holy grail” of autonomous driving. The vehicle can perform all driving tasks under all road, weather, and traffic conditions, without any human intervention. The vehicle is effectively a “driverless” vehicle.
• System Role: The ADS is capable of driving in any scenario that a human driver could.
• Examples: This level of autonomy does not yet exist and is a long-term goal for the industry. A Level 5 vehicle would not need a steering wheel or pedals and could theoretically operate anywhere in the world with a road.