Conditionally automated driving: the S-Class leads the field

Oct 28, 2020

The home office will soon be mobile – including for people behind the wheel. At least if they drive a vehicle bearing the three-pointed star: for Mercedes-Benz is determined to enable, in technical terms, the safe operation of an S-Class driving in conditionally automated mode and to meet the exacting legal requirements for what is known as a Level 3 system[1]. It is expected that from the second half of 2021 the S-Class will be able to drive in conditionally automated mode with the new DRIVE PILOT, in situations where traffic density is high or in tailbacks, on suitable motorway sections in Germany. By taking pressure off the driver, this allows them to undertake secondary activities[2] such as browsing on the internet or dealing with emails in the In-Car Office, and so win extra time. Mercedes-Benz goes another step further when it comes to parking: with the appropriate pre-installation for the INTELLIGENT PARKING PILOT, the S-Class is ready for driverless highly automated parking (Automated Valet Parking; Level 4[3]). For more details see the corresponding chapter. This plan sees Mercedes-Benz taking the crucial step towards conditionally and highly automated driving (SAE Level 3 and Level 4), thereby for the first time offering its customers the possibility in a series production vehicle of handing over the task of driving to the vehicle.

In August 2013, Mercedes-Benz already impressively demonstrated that autonomous or automated driving is not some Utopia, but fundamentally technically possible. At that time, the Mercedes-Benz S 500 INTELLIGENT DRIVE based on the previous S-Class and equipped with near-series technology covered the historic, approx. 100-kilometre Bertha Benz route from Mannheim to Pforzheim completely autonomously. With the DRIVE PILOT, conditionally automated driving at Mercedes-Benz is expected to enter series production from the second half of 2021.

On suitable motorway sections and where traffic density is high, the DRIVE PILOT can offer to take over the driving, initially up to the legally permitted speed of 60 km/h. The controls needed for this are located in the steering wheel rim, on the left and right above the thumb recesses. When the driver activates the DRIVE PILOT, the system controls the speed and distance, and serenely guides the vehicle within its lane. The route profile, events occurring on the route and traffic signs are all assessed and taken into consideration accordingly. The DRIVE PILOT can also recognise unexpected traffic situations, and deal with them autonomously by evasive action within its lane or braking action.

Paradigm change: the vehicle takes control

For the first time, the vehicle takes control while the DRIVE PILOT is active in the Mercedes-Benz S-Class. This is a paradigm change. It is Mercedes-Benz's view that the safe operation of a system of this nature can only be realised with the help of an extended sensor set. This also includes LiDAR ("Light Detection and Ranging": optical measurement of distance and speed), highly precise positioning and an HD map (digital map in high-definition quality). This ensures that the system can confidently hand over safely to the driver even in difficult situations.

While using the DRIVE PILOT, the driver can turn away from what is happening on the road and turn to certain secondary activities, be that communicating with colleagues via In-Car Office, browsing on the internet, or enjoying a relaxing seat massage. This is because in DRIVE PILOT mode, functions can be enabled that are otherwise blocked when driving. However, the driver must always be ready to retake control and immediately resume driving as necessary when the system prompts them to do so, or if it is obvious that the conditions for correct use of the DRIVE PILOT no longer apply.

Conditionally automated driving on suitable motorway sections where traffic density is high

When the vehicle approaches the end of a route section that is suitable for the DRIVE PILOT, for example a tunnel, or if other conditions change, perhaps the weather or the traffic situation (for example when a tailback begins to flow freely), the driver is prompted in good time to retake control. Fundamentally the driver must remain ready to take control and be able to continue driving the vehicle manually within ten seconds – sleeping, looking to the rear for extended periods or even leaving the driver's seat are therefore not possible. To ensure that the driver is able to take control, the cameras of the driver display and MBUX Interior Assist monitor movements of the head and eyelids.

If the driver fails to take back control even after increasingly urgent prompting, e.g. owing to a severe health problem, the DRIVE PILOT brakes the vehicle to a standstill in a controlled manner and with suitable deceleration. At the same time the hazard warning system and, once the vehicle has come to a standstill, the Mercedes-Benz emergency call system are activated and the doors and windows are unlocked, to make access to the interior easier for any first responders. Naturally the driver can also deactivate the DRIVE PILOT at any time without any prompting by the system. This is done via the steering wheel buttons, or by manually intervening in the vehicle's control functions.

With a LiDAR sensor and redundant systems

The DRIVE PILOT is based on the environmental sensors of the Driving Assistance package, and has additional sensors which Mercedes-Benz considers essential for safe conditionally automated driving. These include LiDAR, an additional camera in the rear windscreen and microphones, which are particularly useful for recognising the flashing blue lights and special signals of emergency vehicles. As well as the sensor data, the DRIVE PILOT receives information about the road geometry, route profile, traffic signs and unusual traffic events (e.g. accidents or roadworks) from a digital HD map. This is made available by a back-end connection. The vehicle's location is determined using a highly precise positioning system that goes well beyond the usual GPS systems. The S-Class with the optional DRIVE PILOT also has redundant steering and braking systems and a redundant onboard electrical system, so that it remains manoeuvrable even if one of these systems fails and the safe handover to the driver can be ensured.

A powerful central control unit provides the necessary sophisticated software functions for conditionally automated driving. The image processing, for example, uses future-oriented technologies from the world of artificial intelligence. As part of the sophisticated safety architecture, all algorithms are calculated twice.

The system is constantly improving

The top speed of a system with conditional automation in Germany is restricted by law to 60 km/h. However, the DRIVE PILOT is prepared for the possibility of permitting higher speeds as well via over-the-air updates in the future, where this is technically feasible and the legislative framework allows it. The general introduction of the DRIVE PILOT in other European countries, in the USA and China will follow gradually as the legal situation in each country provides for a surrendering of the driving task.

Legal framework in Germany

In order to be able to allow the customer for the first time to carry out secondary activities during the journey, it is necessary for the Europe-wide harmonised technical approval requirements to be met. However, it also requires national road traffic regulations that allow the driver to use the SAE Level 3 system as intended, including by relinquishing the task of driving. The DRIVE PILOT will initially be offered in Germany because, by opening up its road traffic legislation to Level 3 systems in 2017, Germany was one of the first countries to provide a legal basis for their use. The approval procedure for Europe, which is also necessary for use of the DRIVE PILOT in Germany, is scheduled to be completed towards the middle of next year.

The different levels of automated driving

Following the SAE J3016 standard, the German Association of the Automotive Industry (VDA) defines six different levels of automated driving.

  • Level 0: no automation. The driver performs all driving tasks.
  • Level 1: assisted - driving with assistance systems. The driver always has full control of the vehicle, but can call on support from driving assistance systems for longitudinal or lateral guidance, e.g. from an adaptive cruise control system.
  • Level 2: semi-automated. The driver always has full control of the vehicle, but can call on support from driving assistance systems for longitudinal and lateral guidance or when parking.
  • Level 3: conditionally automated. The driving system with conditional automation takes over dynamic driving tasks when certain parameters apply. A driver who is ready to take control at any time is however still necessary. The driver must take control (with a delay of a few seconds) at all times when prompted to do so by the system.
  • Level 4: highly automated. Under certain circumstances (e.g. selected roads, not in any weather) the vehicle can manage all traffic situations by itself. Depending on the use case, a driver is no longer required (e.g. automated valet parking, people shuttle)
  • Level 5: driverless. The vehicle can perform all driving functions by itself in all circumstances.

[1] SAE Level 3: the automated driving function takes over certain driving tasks. However, a driver is still required. The driver must be ready to take control of the vehicle at all times when prompted to intervene by the vehicle.

[2] The legally permissible secondary activities of the driver depend on the relevant national traffic regulations.

[3] SAE Level 4: Under certain circumstances (e.g. selected roads, not in any weather) the vehicle can manage all traffic situations by itself. No driver is required to be in the vehicle.