Eye-contact is a major element of communication in road traffic. And usually we quite rightly trust that a person who has seen us will give us attention. We do not have this level of relationship and experience with vehicles driving in automated mode. Accordingly Mercedes-Benz considers empathy and trust to be central factors for the acceptance of self-driving vehicles. For people to gain confidence in an automated vehicle, they must be immediately and intuitively able to recognise what it intends to do – so-called "informed confidence". In this respect the ESF 2019 takes human road users very much into consideration. Its sensors – whose development has of course not yet been completed in the experimental vehicle – not only keep an eye on the traffic situation, but also enable the ESF to communicate in all directions. And it not only makes its own intentions clear, it can also warn other road users. Even when even when parked at the roadside and not involved – like a thinking, alert passer-by.

"I have seen you", "I will stay here", "Attention, tailback" or "I'll give way to you" – car drivers constantly give these and other signals to other road users. The ESF 2019 uses clearly visible light signals in turquoise to do the same, thereby instilling informed confidence. There are many means of communication, using: 

• the large front panel,
• LEDs in the sensor unit on the roof, in the indicator repeaters of the exterior mirrors and in the third brake light and
• projections onto the rear window.

Warnings and messages are sent using animations and symbols. Warnings are framed in red according to their urgency, for example in animations on the rear window.

The ESF 2019 clearly indicates e.g. that it will allow a pedestrian to cross the road or make room for a vehicle cutting in. The vehicle can even warn following traffic of hazards that lie ahead.

The ESF 2019 is also equipped with the revolutionary headlamp technology DIGITAL LIGHT, with practically dazzle-free high beam in HD quality and a resolution of more than two million pixels. With the innovative software-controlled DIGITAL LIGHT technology, symbols can also be projected onto the road in HD quality, e.g. as additional information for the driver[3].

As the sensor system of a plug-in hybrid vehicle is not dependent on a running combustion engine for its power supply, it can even keep an eye on the traffic when it is connected to a charging station. So it would be able to warn car drivers of pedestrians who might carelessly wander into the road, or warn a car driver who is turning off about approaching cyclists. At the same time, pedestrians or cyclists can be warned of a hazard: this is because the ESF 2019 shares its knowledge of risks with its direct surroundings, and can therefore protect others against accidents.

Studies have shown that pedestrians like turquoise as a communication colour

360-degree light signals have a special importance when it comes to information for pedestrians. This was a finding from several light studies that Mercedes-Benz conducted in Sindelfingen and at the Test and Technology Centre opened in Immendingen in September 2018, using a cooperative vehicle based on the S‑Class. The studies examined how pedestrians react to differently marked, highly automated vehicles in different traffic situations. It became clear that light signals have a decisive effect on the acceptance of automated vehicles and pedestrians' feeling of safety.

The majority of participants preferred turquoise as the colour of the light signals, and favoured a 360-degree display. Mercedes-Benz is also contributing the results of these studies to the deliberations on "Automated and autonomous driving" by SAE International, an international association of engineers that e.g. develops and proposes norms and standards in the mobility sector. Mercedes-Benz is recommending the colour turquoise, which has not been previously used in the automobile sector, to indicate automated driving mode and communicate with the environment.

Messages to the rear: Projections on the rear window

The rear window of the ESF 2019 plays an important role during interaction with following traffic. To this end the rear window has a membrane which switches from transparent to milky when required, and can then serve as a projection screen for a laser projector in the luggage compartment. This can not only project symbols and text, but even the image of the front camera onto the rear window.

For example, if the ESF allows a pedestrian to cross the road in front of it, the situation is explained to following traffic by a projection onto the rear window: A symbol indicates why the ESF is stopping, and subsequent projection of the camera image shows the pedestrian in front of the ESF to give vehicles behind a clear understanding. The ESF therefore communicates its behaviour clearly, and following traffic is not tempted to try overtaking.

[3] New technologies must always meet the legal requirements of the different markets, and must therefore be adapted accordingly. We are currently examining the approval situation in this respect.