The terms “self-driving” and “autonomous” seem simple and self-explanatory, but what is not so clear is that there are, in fact, distinct degrees of autonomy instead of a one-size-fits-all term. As varying levels of driver-assistance technology entered the market from an equally varied mix of manufacturers, a standardized guide to the nomenclature and their definitions would have been helpful. But none existed.
In 2013, the U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) created a set of guidelines regarding terminology specific to automated vehicles. Similarly, the following year, the Society of Automotive Engineers (SAE) International, a non-profit global association of engineering professionals, developed its own classification regarding Automated Driving Systems (ADS) that NHTSA itself would eventually adopt in 2016.
The SAE standard (officially known as J3016) defines a vehicle’s level of autonomy from 0 to 5 based on the number of advanced driver-assistance systems (ADAS) utilized. For example, Levels 0-2 require a human driver to be present and able to take control of the vehicle, even when equipped with an ADAS. Levels 3-5 mean the vehicle monitors the driving environment and can also intervene in dynamic situations should a human driver, if present, fail to react to system alerts.
Level 0 – No Automation
Just as the number suggests, vehicles that fall under Level 0 have zero autonomous features. A human driver must perform all the dynamic driving tasks. These vehicles may be equipped with assistive technology and safety warnings, like fixed-speed cruise control and blind-spot monitoring, but the physical acts of accelerating, decelerating, and steering are always handled by a human driver.
Example: Typically, any 2000-model year vehicle and older will be Level 0.
Level 1 – Driver Assistance
A Level 1 vehicle has at least one ADAS that can manipulate speed and steering inputs, but all other driving tasks such as lane changing and turning remain the responsibility of a human driver. Technology like adaptive cruise control (ACC), where the vehicle maintains a set speed but can also decelerate and even come to a complete stop, is convenient in bumper-to-bumper traffic, but entering and exiting a highway, for example, is still handled by a human driver.
Example: Any vehicle equipped with an ADAS that controls any aspect of acceleration, deceleration, and braking. This includes but is not limited to ACC, lane-keeping assist (LKA), automatic emergency braking (AEB), and parking assist.
Level 2 – Partial Automation
Qualifying vehicles are equipped with at least two semi-autonomous features that work together in fixed scenarios. For instance, a combination of ACC and lane-keeping assist (LKA) can minimize driver fatigue on long drives. However, these systems will deactivate if a human driver’s hand is not detected on the steering wheel after a certain amount of time – usually within 20 seconds. Even with Level 2 “self-parking” technology, a human driver must still be present to take control as needed.
Example: Systems like Cadillac Super Cruise, Nissan ProPilot Assist, Tesla Autopilot, and Volvo IntelliSafe Autopilot, although impressive, are Level 2 ADAS. And that means you can’t check email, or watch movies, or Snapchat instead of paying attention.
Level 3 – Conditional Automation
Where the previous levels mean a vehicle’s ADAS can handle certain operation modes, a human driver is still held accountable for monitoring the driving situation and taking over if necessary. At Level 3, both the driving dynamics and observation of surroundings are handled by the ADAS. But the systems are still bound by certain conditions, such as mapped roads and divided highways with physical barriers. A human driver also must remain alert behind the wheel as a backup.
Example: The 2019 Audi A8 is the first Level 3 autonomous vehicle available to consumers – who reside in Europe. Called Traffic Jam Pilot, the system can negotiate traffic at speeds up to 35 mph without a human driver monitoring it. However, due to a lack of federal regulations, Audi will not release this ADAS in the U.S. market just yet.
Level 4 – High Automation
Only at Level 4 is a human driver or presence unnecessary. The ADAS will handle all aspects of driving and is capable of completing trips without any human intervention. However, a Level 4 vehicle will still have some restrictions in place, such as speed limits and geofencing, which means they are confined within a software-enabled, location-based area.
Example: There are no Level 4 vehicles currently available for purchase, but Waymo One, a 24-hour, self-driving vehicle service in the greater Phoenix area, is available to a select group of members as part of Waymo’s real-world testing. And although the vehicle does all the maneuvering, safety drivers are present during all Waymo One trips.
Level 5 – Full Automation
This would be peak autonomy – just like in the movies! And, no driver means no steering wheel, no pedals, and no shifter are needed. Essentially, everyone in the vehicle would be considered a passenger. At Level 5, there would be no limitations either, geographical or otherwise. However, this level of autonomy would require not only a massive amount of advanced software and sensors but also an infrastructure that can support vehicle-to-everything (V2X) communications.
Example: Any sci-fi show or film because, for now, fiction is the closest reality of fully autonomous vehicles. From federal laws to municipal groundwork, many factors remain at play and questions unanswered regarding a utopian world of truly driverless vehicles.