How should Autonomous Vehicles communicate?
A survey of User Experience in the Communication between Autonomous Vehicles and Road Users
By 2030, AVs will be manufactured in mass production at autonomous levels 4 and 5 and will account for 25% of new vehicles in the EU.
In view of the new technology of self-propelled vehicles, new communication approaches are appearing in the traffic environment between autonomous vehicles and other road users, i.e. other motorists, cyclists and pedestrians. A review of the requirements for this changed communication is therefore necessary. An investigation by means of a focus group has contributed to the determination of functional requirements as well as the most suitable form of communication.
Due to the non-existing driver and consequently a lack of eye contact or other reaction in the interaction and also due to the lack of experience with the new technology, there is an uneasiness and insecurity among the participants regarding the interaction with autonomous vehicles in road traffic.
Pedestrians and cyclists have a much greater feeling of insecurity than car drivers, which is why they should be prioritized here. In order to meet the requirement for safety, technical communication interfaces are needed through modalities to communicate the driving mode, feedback on awareness and vehicle status/intention. In addition, the requirement for standardized and as few as possible and only useful signals became clear in order to avoid an information overload.
With regard to human-machine interaction (HMI), there are various modalities (technological forms and means) and codalities (forms of information representation) which might be considered. They already show up in future concepts of some OEMs or patents of technology companies, such as Google.
The modalities as possible modes of communication
Projections: A laser projects visual illustrations directly onto the street.
Display: A display on the front of the vehicle shows information.
LED elements: Also mounted at the front of the vehicle or at the rear, several hundred LEDs form a holistic display.
Auditory cues: Audio signals through specific voice outputs or sounds for warnings, commands or other messages.
Mobile Devices: A direct notification from the vehicle to e.g. the smartphone, the headphones, the key fob or transponder or the belt via audio, visualization or haptic feedback.
Gestures: The external road user can take on an active role and transmit information to the AV based on camera analysis of the hand gestures or body movements.
Visual modalities have proven to be the most popular. In particular, a combination of projection and display or LEDs appears to be the most appropriate, as this is the best way to address the external road user in a specific situation. For example, projections seem to be useful in low speed situations, whereas LEDs seem to be suitable at faster speeds.
Auditory cues should be treated with caution. They should be considered in the context of the visually impaired or as an additional warning in hazardous situations. In everyday life, however, they are classified as problematic. Due to the variety of gestures and the difficult implementation, gesture control can also be regarded as an addition in order to make the vehicle understand that one would like to cross the road. This can satisfy the pedestrian’s need for autonomy. Mobile devices should not be the focus of a communication concept. They are generally unpopular among the participants, as there is only insufficient trust in the reliability of signal reaching and moreover they are considered as impractical.
The codalities used by the modalities
Color cues: Different color meanings and symbolic characters can be used to display information.
Text: Specific text messages can be used to convey concrete information and prompts.
Symbols: Due to associated meanings, symbols also offer the possibility of displaying content.
Motion: Visual movement graphics are intended to indicate behaviour patterns to external road users.
Human-like animations: Digital eyes or animations, such as facial expressions or hand movements, can also be used for communication.
The preference in terms of codalities is made up of a combination of several codalities. Symbols are particularly popular because they can be quickly grasped in the street environment and are usually interpreted intuitively, as well as color cues. Text and motion may only be seen as an additional supplement, e.g. to symbols. Independent use can lead to problems with perception and comprehension. The human-like animations are perceived by the test persons as superfluous, since they do not provide any helpful added value for them.
The importance of a discreet, minimalist and pragmatic message design must be emphasized regarding all signals. Only contents which are truly necessary should be conveyed and too many different states as well as too much movement, color, etc. should be avoided.
These findings show how difficult communication can be and how important it is to develop an appropriate concept. The needs and preferences of the test persons should therefore not be disregarded in future communication concepts for autonomous vehicles. Further investigations in this direction are advisable to deepen the functional requirements and exact design conditions. However, taking these insights into consideration by the OEMs can already mean added value for them, as they can align their concepts according to the results.
Sources: PwC, Roland Berger Focus, Bachelorthesis “User Experience Aspekte bei der Kommunikation zwischen autonomen Fahrzeugen und externen Verkehrsteilnehmern” by Antonia Völkers
