The 5 stages of autonomous driving

The advances made by Google and Tesla have made autonomous driving the talk of the town. Although the term appears so frequently in the media, many people are not even aware of what is actually hidden behind the term. Autonomous driving is not just the romanticized idea of letting go of the steering wheel and letting the car chauffeur you to your desired destination. Rather, it is an umbrella term that stands for a wide variety of forms of assistance in driving. In this article, we highlight SAE's five levels of automated driving and show where we currently are on this scale.

What is autonomous driving? One potential answer to this question might be "when you’re able to let go of the steering wheel and let the car do the driving." While this answer may be factually correct, it covers only a small part of what autonomous driving really is. It is not just one function, program or module that you can install in your car at will. Rather, autonomous driving is a hypernym for many smaller and larger innovations and technologies, working together to make people's lives easier. It starts with small tools like adaptive cruise control, or lane departure warning systems, which will warn the driver but don’t take control. These small, useful tools are already part of everyday life for many drivers and, depending on the standards, might even be taken for granted. They count as assistants, meaning they are computer-controlled programs that assist the driver using sensor data and algorithms, in order to help with various tasks. It should therefore be noted that both the comparatively simple lane departure warning system and fully automated driving, in which the driver can completely turn his back on what is happening, count as autonomous driving in the vernacular. Nonetheless, these examples are very far apart on a scale of functionality and complexity. So how does the industry differentiate between simple assistants and fully self-acting vehicles? This is where SAE International's five levels of automated driving come into play.

The five levels of SAE International

For an industry to cooperate and grow together, a common terminology is needed. In 2014, SAE International took on the challenge to create a definition and communication base for the development of automated vehicles. The term SAE stands for Society of Automotive Engineers. It’s an organization of automotive experts that was founded in 1905 and is dedicated to advancing the technological progress of the automobile.

The fruits of this gathering of industry experts are the five levels of automated driving, which is a classification model, enabling experts to sort different functionalities into the namesake five levels. With each level, complexity and automation increase while manual operation of the vehicle decreases. At levels one and two, experts speak of driver support systems. As the name suggests, these are systems that provide the driver with information but do not actively intervene, or do so only to a limited extent. The next step is automated driving, which takes place at levels three and four. Here, the person driving can turn away from the steering wheel in certain situations. Genuine autonomous driving only applies to Level 5, according to the SAE International system. The system has become the industry standard because of its comprehensible and precise structure. In the following graphic, the five stages are clearly summarized and presented.


Level 1 - Assisted Driving:

  • At Level 1, the driver must maintain control of the vehicle at all times and keep an eye on traffic.
  • Systems, such as cruise control or distance assist, can assist the driver, but they do not take control of the vehicle and the driver remains liable.


Level 2 - Partially Automated Driving:

  • The vehicle can partially perform some tasks by itself, such as parking or braking and accelerating on the highway.
  • Meanwhile, the driver can temporarily take his hands off the steering wheel.
  • However, the driver remains in charge, must monitor the assistance systems at all times to take back control of the vehicle in an emergency.


Level 3 - Highly automated driving:

  • In certain traffic situations, such as overtaking, braking or accelerating on the highway, the vehicle can drive autonomously for an extended period of time.
  • The driver may temporarily turn away from the driving action to do other things such as reading or checking their smartphone.
  • However, the driver must still be prepared to take the wheel again at any time.


Level 4 - Fully automated driving:

  • The vehicle takes over almost all tasks and the driver becomes a passenger.
  • Passengers are allowed to completely turn their backs on the driving action.
  • Driving without passengers becomes possible.
  • Passengers are no longer liable for traffic violations or damages.


Level 5 - Autonomous driving:

  • Truly autonomous driving does not occur until Level 5, according to the SAE International system.
  • Level 5 represents the perfection of automated driving.
  • Even the most complex traffic situations can be mastered by the system without any problems.
  • There are now only passengers in a car.



A look into the future - The threshold to Level 3

When looking at the graphic above, which stage have we currently reached? In fact, we are at a turning point. After years of innovation, testing and development, the industry has reached Level 3 with Mercedes' highway traffic jam pilot. Countless companies are also working hard to bring fully automated driving into everyday life as well, allowing people to take their minds off what's happening on the road. While this is already a reality in the test vehicles of many companies, the algorithms are still lacking experience in unusual situations, such as construction sites or with a broken traffic light. Only when the systems make the right decisions even in such rare scenarios, they will be ready for the customer. However, further developments are taking place not only on a practical level, but also from a theoretical point of view. SAE International recently updated their five levels in response to latest trends and advances in the automotive industry. Among other things, remote controlled cars and different vehicle types (e.g., conventional and hybrid vehicles) were examined and embedded in the system. This example illustrates that although the five levels of automated driving gave the automotive industry more structure and unified many aspects, there are still and will always be ideas and technologies left to explore and to integrate into the given theoretical model.

While it is already possible at Level 4 that the driver can completely turn away from the driving action and for vehicles to act completely driverless, the vision of the 5th level is to bring all of this to perfection. On Level 5, all vehicles are able to navigate in every conceivable scenario without assistance, and all people in the vehicle thus become passengers. With the 5th level, the dream to sit back and hand over all responsibility to the vehicle, will come true. Until then, however, the industry still has many years of research and development ahead of it. Currently, experts believe that Level 4 vehicles will not be ready for serial production until 2030. It is currently unclear when Level 5 will be in reach.

No matter how long the road to Level 5 may be, LiDAR technology is the key. With the ibeoNEXT on board, Ibeo test vehicles are already traveling through Hamburg, Berlin and Beijing to test Level 3 and 4 systems. The current goal is to use the ibeoNEXT to achieve serial production readiness for Level 3 automated driving and afterwards to devote all resources to reach Level 4. But no matter the goal, the safety of drivers and passengers is and always will be Ibeo's top priority.

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