What are the 6 levels of autonomous vehicles?

In our dreams, when thinking about driverless vehicles, we tend to imagine a car which requires no input by the driver, and literally drives itself, but it isn’t the actual case.

In reality, even the latest generation of vehicles, technologically more advanced, are not yet at those levels of efficiency, above all regarding the safety of drivers, passengers and pedestrians, and have limited autonomous functionality despite being much more sophisticated compared to those of just a few years ago.

The level to which a vehicle can be described as autonomous is set by the SAE International (Society of Automotive Engineers) in a document entitled “Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles”.

Let’s take a look at various levels of autonomy of vehicles as defined by the SAE.

The 6 levels of autonomy as defined by the SAE

The above-mentioned documentation describes the autonomy systems of motor vehicles which execute either part or all of dynamic driving activities on a continuous basis.

The SAE has thus defined 6 different levels of autonomous driving:

  1. Level 0: no driving automation
  2. Level 1: driver assistance
  3. Level 2: partial driving automation
  4. Level 3: conditional driving automation
  5. Level 4: high driving automation
  6. Level 5: full driving automation

Let’s take deep-dive in these levels to understand their differences.

Level 0: no driving automation

As the title suggests at this level the vehicle possesses no automated driving features, but that doesn’t necessarily exclude driver assistance features.

Indeed, the driving experience is entirely in the hands of the driver, but the vehicle is equipped with a system which provides momentary driving assistance, such as warning signals or emergency safety actions. The driver therefore must drive the vehicle and monitor any possible warnings or safety activities, and thus the driver is responsible for braking, steering, accelerating etc.

The following technologies come under this category:

  • ABS
  • ESP
  • cruise control
  • blind spot warning
  • automatic emergency braking
  • frontal collision warning
  • lane departure warning

Driving is 100% manual.

Level 1: driver assistance

Moving up one level, we are now talking about vehicles equipped with a system which supplies constant assistance during acceleration, braking and steering, whilst the driver is both involved and attentive.

Also in this instance therefore, the driver has the task of driving the vehicle and monitoring the system, which however - if activated - can perform steering, acceleration and braking functions.

Here are some examples of technologies installed in Level 1 vehicles:

  • electronic adaptive speed regulator, or adaptive cruise control
  • lane keeping assistance or lane centring assistance

Compared to Level 0, these vehicles offer greater support to the driver, who however must always play an active role in driving.

Level 2: partial driving automation

Level 2 applies to a large share of the autonomous vehicles that are on the market today.

They are equipped with advanced driving assistance systems (ADAS), and this provides continual assistance both regarding acceleration/braking and in steering, whilst the driver is 100% attentive and involved with the possibility however of handing over control of combined longitudinal and lateral functions.

When active, the system can control steering, acceleration and braking. Still, levels 0, 1 and 2 require the driver to be involved and aware, and constantly monitoring the functionality of the support features offered by the systems installed.

Level 3: conditional driving automation

At Level 3 we are definitely at a more advanced level, which is not widespread in the market yet, and offers conditional driving automation functions, whenever the driver allows the system to take over.

Simply put, that means that when activated the system carries out all aspects of the driving functions, however the driver must be seated in the driver’s position and ready to take control when necessary or requested.

Livel 4: high driving automation

The essential difference between Level 3 and Level 4 lies in the fact that the systems which vehicles at this level are equipped with are able to intervene in the instance of a malfunction without necessarily involving the driver.

The driver however, still has the power to take control of the vehicle manually.

Current regulations allow these kinds of vehicles to be used only in very specific and well-defined circumstances, for example in city centres where speed limits are extremely low. For this reason, they are generally destined to be used aboard ride sharing vehicles.

Level 5: full driving automation

Level 5 vehicles, according to SAE classification, reach the very highest level of automation due the advanced technologies employed.

Indeed, they require no human intervention and not even emergency manual intervention, whatever the driving conditions or the state of the roads. For this reason, the vehicles are not equipped with pedals or a steering wheel.

Therefore, a person could come on board and literally undertake any activity whilst totally ignoring the driving situation.

Here follows a useful infographic developed by SAE which sums up the 6 levels of autonomous driving.