Levels 1 and 2 are “driving-mode specific” autonomous features that assist in steering, acceleration and deceleration.Level 1 can be thought of as radar or active cruise control working in conjunction with lane guidance. These features are currently fitted to many existing cars including most Subaru and Mazda models and an increasing number of Europeans.Level 2 is more advanced, where the computer controls most of the driving experience. The new Mercedes-Benz E-Class achieves Level 2 autonomy with its “Drive Pilot” autonomous cruise control feature. This will steer, keep lanes and change lanes safely with only prompts (indicator stalk, cruise control buttons) from the driver. Should the driver disengage from the wheel at any time the vehicle will come to a complete stop. In a nutshell, you need to keep your hands on the wheel in readiness to take over.Levels 3–5This is where things get more interesting. The key defining factor the SAE use to split Levels 0-2 from 3-5 for is whether the car is capable of ‘monitoring the driving environment.’ – That is, where the computer is in control of all the main driving functions and able to respond to changing surroundings.At Level 3 the car may drive and monitor the environment itself, but requires a human to be present to perform inputs if requested (via dashboard prompt). This means you can take your hands off the wheel and the car will continue unaided with a degree of ability to manage varying road conditions. It may need human input in emergencies or while navigating to a destination. Beyond active cruise control, a Level 3 car is able to drive you in more complex traffic conditions than the free-flowing motorway environment required by lesser levels.Level 4 does not require a human to input driving actions, even in an emergency. The car is able to respond to all situations on the road and guides itself via a navigation system and sensors. The autonomous functionality still needs to be activated by a human at the start of a journey and the car may request driver intervention, but does not need to depend on it.For example, the car may ask you if you want to take an alternate route, if you do not respond in time the car will decide automatically.Level 5 – ‘Full Automation’ – The car does not require a driver to be present at all. A driver is not required for emergencies or any guidance. The car is autonomous from the moment you sit in it, and is able to be summoned remotely to a location without any occupants. Sick of driving the kids to school? Your Level 5 car could do that for you. Scary, eh?Tesla’s full self-driving capability claim implies that the new EVs are the first production cars capable of Level 5 autonomy.