IEEE Consumer Electronics Magazine - September/October 2019 - 94

Special Section on Human Centric AR&VR Display and Human Interface Technologies for Automobile

Figure 1. Sequence diagram "ToVC" that realizes
the extended use cases.

difficult to continue, including the interactions
between the driver and ADS.
A key challenge for the ToVC in conditional
automated driving is the realization of proper
interaction between the driver and ADS. It is
therefore necessary to capture the interaction,
especially between them. To identify how the
ADS, the driver, and other external systems
interact by exchanging message, the extended
use case was modeled in sequence diagram
(Figure 1) and, in particular, the functionalities
of HMI can be defined within their interaction.
The driver requests the ADS to identify driver's
own state or behavior. The driver also requests
the ADS to provide information regarding the
ToVC, and the ADS then replies with the information requested by the driver. The driver takes
actions to regain control of the vehicle while
monitoring the information provided by the ADS
and directly perceiving the driving environment
and the vehicle state. Driver's virtual requests to
the ADS here were used to define the functionalities required by a system based on requests
from the external. Actually, when the ToVC
starts, the ADS may execute the ToVC regardless
of the driver's requests.
Based on the interaction between the driver
and the ADS, it is possible to explicitly capture
the functionality of the HMI. As shown in
Figure 1, for a successful ToVC between the
driver and the ADS, it is desired that the

functionality of the HMI enable the driver and
the ADS to interact with each other by providing the driver with information and identifying
driver's state or behaviors.
As a result of modeling scenarios related to
the use cases using sequence diagrams, the
interaction between the constituent systems
within the ODD was identified clearly. Figure 2
shows the structural relations between the constituent systems of the SoS involving automated
driving vehicles. The insight from Figure 2 may
be that the relationship between the driver and
the ADS is asymmetric. For example, the driver
perceives driving environment by using the
visual organs, but ADS uses information
exchange with external systems as well as sensors to obtain more accurate driving environment information. Thus, the differences in the
amount of information that the driver and ADS
acquire can cause discrepancies between the
driver's understanding of the driving environment and the information furnished by the ADS.
Moreover, degradation of capability such as a
delay in or lack of driver's perception of the
information may cause the driver's misunderstanding of ADS actions.
From the viewpoint of the context of the SoS
involving automated vehicles, it is difficult for
the functionality of HMI as previously mentioned
to address problems that can be caused by the
asymmetry in the amount of information
obtained by the driver and the ADS, respectively.
This is because providing information through
HMI is not sufficient to ensure that the driver
and the ADS have a common understanding.
Therefore, it is necessary to aid both the ADS
and driver narrow the differences in decisionmaking between them through a common understanding of information. For example, the HMI
should enhance the driver's understanding of
information regarding external systems, the
ADS, and the driver's own. Furthermore, the
HMI should also inform the ADS of the information regarding the driver for the ADS to understand the driver's capability to control the
vehicle, and the driver's behavioral intentions.
Particularly, given the functionalities of the
HMI enhance the driver's understanding, it is
possible to consider a warning of the risk of accidents with the external system around vehicles,

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IEEE Consumer Electronics Magazine - September/October 2019

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