The Society of Automotive Engineers (SAE) is the pre-eminent standards development organisation for the automotive industry. Currently, the SAE classifies vehicles into six different levels of autonomy. Paraphrased, these are:
- Level 0: No driving automation. The driver is responsible for all tasks.
- Level 1: Driver assistance technologies. Technologies such as adaptive cruise control can control either acceleration/braking or steering, but not both. These are assistance technologies only, and the driver must control the vehicle.
- Level 2: Partial driving automation. The car can sustain control of acceleration/braking and steering only within specific environments (e.g. a motorway with clearly marked lanes). The driver is expected to remain alert and able to intervene at any time. The driver is also expected to supervise the automation system and to handle any hazards or other adverse events that may occur.
- Level 3: Conditional driving automation. The car can sustain control of all driving tasks (acceleration/braking, steering and other driving tasks such as changing lanes) only within specific environments (e.g. a motorway with clearly marked lanes). However, the driver is expected to respond and take control of the vehicle if the car warns the driver, or if the automated driving system fails.
- Level 4: High driving automation. The car can sustain control of all driving tasks (acceleration/braking, steering and other driving tasks such as changing lanes) only within a specific environment (e.g. a motorway with clearly marked lanes). Within this specified environment, there is no expectation that a driver will intervene.
- Level 5: Full driving automation. The car can sustain control of all driving tasks in all environments, unconditionally. There is no expectation that a driver will intervene.
The SAE standard provides the following table for autonomous driving (paraphrased above):
The main problem with this system is the terminology. In the ordinary sense of the word, 'autonomous' means having the ability to independently control oneself, free from interference. When applied to Level 2 and Level 3 vehicles, this is clearly not true, as both types of vehicles can function with only limited independence, in specific environments, and operate with the expectation that a driver can intervene if things turn awry.
This has consequences in relation to how the automotive industry markets autonomous vehicles, and how customers perceive them.
Audi's misleading description of the A8 having 'Level 3' autonomy
Audi's press materials describe the A8's autonomous driving system as follows:
The errors in this press release begin with the description of the A8's capability for 'highly automated driving.' As per the SAE standard, high driving automation is classified as Level 4. Whilst the term 'highly automated driving' has an element of subjectivity to it, and Audi is free to market the A8 as it sees fit, it's misleading to obfuscate the subjective 'highly automated driving' with the term 'high driving automation', that has a defined meaning that the A8 does not meet as per the SAE standard.
Another error lies within Audi's substantive description of the A8's autonomous driving capability. Let's break down Audi's description, according to the SAE criteria:
- Driving tasks performed (Dynamic Driving Task, or DDT): "The traffic jam pilot manages starting, accelerating, steering and braking. It can also handle critical situations such as vehicles cutting in closely in front."
- Operational environment (Operational Design Domain, or ODD): "On freeways and highways where a physical barrier separates the two carriageways, the system takes over the driving task if the car is traveling at less than 60 km/h (37.3 mph) in nose-to-tail traffic."
- Extent of human driver involvement required (DDT fallback): "During highly automated travel a small camera in the driving area detects if the driver tires or falls sleep. If that happens, a multi-stage warning is given. As soon as the speed rises above 60 km/h (37.3 mph) or the line of vehicles breaks up, the traffic jam pilot informs the driver that they need to take charge of driving once again. If they ignore this prompt and the subsequent warnings, the new A8 is braked to a standstill."
For a car to have Level 3 automation, the SAE suggests that it must have control of all driving tasks within the specified operating environment. Audi suggests the A8 manages starting, accelerating, steering and braking, on dual-carriage highways with a separating physical barrier, when the car is travelling at less than 60 km/h. However, the company makes no mention of other DDTs such as changing or merging lanes that are often necessary in the operating environment that Audi describes. Furthermore, whilst the SAE standard doesn't prescribe any suggestions for the type of ODDs that Level 3 vehicles should be able to operate in, the operating environment of Audi's autonomous driving system is remarkably limited. 60 km/h is a very low operational speed limit, and effectively means that Audi's system works only in stop-start traffic jams on highways. In light of the very limited scenarios that Audi's system can actually work in, it is not significantly different from existing adaptive cruise and lane-keep assist systems widely available today.
The SAE should rephrase the six levels of autonomous driving, such that terms such as 'autonomous vehicles' and 'driving automation' apply only to Level 4 and Level 5 vehicles. The technologies offered in Level 2 and Level 3 vehicles are, for all practical purposes, driver assistance technologies rather than autonomous driving technologies. Categorising these vehicles as having 'driving automation', when in most practical situations they require human supervision, can create the potential for misleading marketing, as evidenced by the Audi A8 above, and consequently create customer confusion and overconfidence in the technology available today. Ultimately, there is no commercially available autonomous car on sale today.