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-assist technology enters the market from an equally varied mix of manufacturers, a standard guide to the nomenclature and their definitions would be helpful.
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) 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 utilized. For example, Levels 0-2 require a human driver to be present and able to take control of the vehicle. Levels 3-5 mean the vehicle monitors the driving environment and intervenes 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 come with assists and safety warnings, like fixed-speed cruise control and blind-spot monitoring, but the acceleration, deceleration, and steering are under a driver’s control. Typically, any 2000-model year vehicle and older is Level 0.
Level 1 – Driver Assistance
A Level 1 vehicle has at least one driver-assist that can manipulate speed and steering inputs, but all other driving tasks such as lane changing and turning remain the responsibility of the driver. Technology like adaptive cruise control, which maintains a set speed but also decelerates and even comes to a stop, is convenient in bumper-to-bumper traffic. But the driver must still control entering and exiting a highway.
Level 1 vehicles employ driver assists that control any aspect of acceleration, deceleration, and braking. This includes but is not limited to adaptive cruise control, lane-keeping assist, automatic emergency braking, and parking assist.
Level 2 – Partial Autonomous Driving
Qualifying vehicles are equipped with at least two semi-autonomous features that work together in fixed scenarios. For instance, a combination of adaptive cruise and lane-keeping assist can minimize driver fatigue on long drives. However, these systems will deactivate if a 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, the driver must still be present to take control as needed.
Systems like Cadillac Super Cruise, Nissan ProPilot Assist, Tesla Autopilot, and Volvo IntelliSafe Autopilot, although impressive, are Level 2 systems. 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 assists can handle certain operations, a driver is still must monitor the driving situation and take over if necessary. At Level 3, both the driving dynamics and observation of surroundings are handled by automated driving systems. But the technology is only autonomous under certain conditions, such as mapped roads and divided highways with physical barriers. A driver also must remain alert behind the wheel as a backup.
The 2019 Audi A8 is the first Level 3 autonomous vehicle available to consumers in Europe. Called Traffic Jam Pilot, the system can negotiate traffic at speeds up to 35 mph without a driver monitoring it. However, due to a lack of federal regulations, Audi will not bring Traffic Jam Pilot to the U.S. market just yet.
Level 4 – High Automation
Only at Level 4 is a human driver or presence unnecessary. The autonomous driving system will handle all aspects of driving and is capable of completing trips without human intervention. However, a Level 4 vehicle will still operate under restrictions including speed limits and areas defined by geofencing. These vehicles are confined within a software-enabled, location-based area.
There are no Level 4 vehicles currently available for purchase. However, Waymo One, a 24-hour, self-driving vehicle service in the greater Phoenix area, operates as a real-world test. And although the vehicle does all the maneuvering, safety drivers are present during all Waymo One trips.
Level 5 – Full Autonomous Driving
This would be peak autonomy – just like in the movies. Having no driver means no steering wheel, no pedals, and no shifter. Essentially, everyone in the vehicle is a passenger. At Level 5, there would be no limitations either, geographical or otherwise. However, this level of autonomy requires a massive amount of advanced software and sensors. It also needs an infrastructure that can support vehicle-to-everything (V2X) communications.
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.
