Which levels of driving automation can be distinguished?

We most often distinguish different levels of self-driving vehicles by referring to the so-called SAE Levels of Driving Automation [4]. This classification consists of six levels which are based on the extent to which technology supports the driving task: from level 0, where only the driver carries out the driving task, to level 5, where the vehicle completely carries out the driving task. Below the six levels are explained:

	Level 0: Only the driver carries out the driving task. The vehicle may be equipped with systems that provide alerts and/or that momentarily intervene. Examples are alerts when the vehicle leaves its lane (Lane Departure Warning) or a system for emergency braking (Autonomous Emergency Brake). Currently, most vehicles on the road belong to this category (see SWOV fact sheet Intelligent transport and advanced driver assistance systems (ITS and ADAS)). Level 1: The vehicle can steer or brake/accelerate by itself. This concerns support technology that helps keep the car in its lane (Lane Keeping System) or keep a safe distance to the vehicle in front (Adaptive Cruise Control) (see SWOV fact sheet Intelligent transport and advanced driver assistance systems (ITS and ADAS)). The driver, however, has to continuously monitor whether the vehicle carries out the automated task properly, and has to intervene immediately if necessary. Level 2: At the previous level, one of two support technologies could be active. At level 2, both support technologies are active. This implies that the vehicle can steer and brake/accelerate. At this level, once more, the driver has to continuously monitor the automated task, and has to intervene immediately if necessary. The Tesla Autopilot [5] is an example of a Level 2 vehicle.
	Level 3: The vehicle is able to drive by itself in specific conditions. The conditions may, for instance, refer to road type, weather, and traffic intensity. If the specific conditions no longer apply, the driver has to take over the driving task. Think, for example, of a vehicle that can usually drive by itself, but is no longer able to do so in heavy rain or in conditions where road markings are invisible.
	Level 4: As was the case at the previous level, the vehicle is only able to drive by itself in specific conditions. But at level 4, the driver does not need to take over the driving task when the specific conditions no longer apply. The vehicle can park itself, for example, before the specific conditions cease to be applicable. Level 5: At the top level, the vehicle is completely self-driving, implying that it can drive itself in all circumstances.