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Motion SIckness in Automated Vehicles



In an automated vehicle, the driver is a passenger. It is said that the driver seldom gets motion sickness or carsickness compared to passengers. This suggests that motion sickness could be a problem in highly automated vehicles. Other changes such as seating posture or engaging in non-driving tasks can occur by introducing automated driving. In addition to such changes for drivers, changes in vehicle systems occur that are caused by the automated system taking control of the vehicle. This paper discusses motion sickness in automated driving by dividing the changes for drivers and those in vehicles. The countermeasures are also discussed from both viewpoints with emphasis on a vehicle control method that minimizes motion sickness based on a mathematical model of motion sickness.
The technological aspects of automated vehicles
or self-driving cars have been actively studied in re-
cent years. The human factors in automated vehicles
have also been studied. These research studies in-
clude a driver’s response when the driving authority
is being transferred back to the driver (Louw et al.
2015)(Blanco et al. 2015) and the driver’s trust in
automated driving (Abe et al. 2015).
In this study, the automated vehicle was assumed to
be operated at level 3 or higher in SAE-J3016 levels
of automated driving, in which the driver does not
need to attend to the vehicle control or even monitor
the traffic environment. In automated vehicles, the
driver becomes a passenger. It is known that drivers
seldom get carsickness compared to passengers.
Thus, it is thought that the drivers of automated ve-
hicles will tend to experience motion sickness more
Originally, automated vehicles began to be devel-
oped to increase the driver’s comfort and productivi-
ty during transportation (Diels & Bos 2015). An in-
crease in the occurrence of motion sickness during
automated driving has a significantly negative im-
pact on this original purpose. However, few studies
have been performed on motion sickness in auto-
mated driving. Diels et al. discussed factors relating
to motion sickness for automated driving in specific
potential scenarios involving a change for drivers
and proposed countermeasures for decreasing the
occurrence of motion sickness (Diels & Bos 2015).
Sivak et al. estimated the number of passengers who
would experience carsickness during automated
driving based on survey results about activities that
people would like to do in an automated vehicle as
well as some potential countermeasures (Sivak &
Schoettle 2015). In addition to such changes for
drivers, the vehicle system also undergoes certain
changes that are caused by the automated system
taking control of the vehicle.
Therefore, this paper discusses motion sickness in
automated driving by dividing the changes for driv-
ers and those in the vehicles. The countermeasures
will be also discussed from both viewpoints. A vehi-
cle control method that minimizes motion sickness
will be introduced based on a mathematical model of
motion sickness. An individual who is released from
vehicle operation is referred to as an “occupant” in
this paper even if he/she is expected to take over the
driving operation from the vehicle automation when
When drivers are relieved of the driving operations
in automated vehicles, the following two changes
1) The individual who previously drove the car is
transformed into a passenger;
Motion Sickness in Automated Vehicles
T. Wada
Ritsumeikan University, Kusatsu, Shiga
ABSTRACT: In an automated vehicle, the driver is a passenger. It is said that the driver seldom gets motion
sickness or carsickness compared to passengers. This suggests that motion sickness could be a problem in
highly automated vehicles. Other changes such as seating posture or engaging in non-driving tasks can occur
by introducing automated driving. In addition to such changes for drivers, changes in vehicle systems occur
that are caused by the automated system taking control of the vehicle. This paper discusses motion sickness in
automated driving by dividing the changes for drivers and those in vehicles. The countermeasures are also
discussed from both viewpoints with emphasis on a vehicle control method that minimizes motion sickness
based on a mathematical model of motion sickness.
2) The person who controls the vehicle is replaced
by the automation.
The possibility of motion sickness in those riding
in an automated vehicle is discussed based on these
two points (Table 1).
Table 1 Potential effects of automated vehicle on
motion sickness
What is changed Examples of chang-
Possible risk factors
of motion sickness
for drivers
caused by
being re-
lieved of
the driving
Difference by
presence or
absence of
the driving
Difference between
driver and passen-
(control, activity,
visual information,
- Decrease of opera-
tion activity and an-
Changes in posture
and body move-
ments (e.g., Seating
in rear-facing posi-
- Decrease in antici-
pation of road ge-
ometry ahead
Increase of
Addition of non-
driving tasks
(reading documents,
tablet operation,
- Decrease in antici-
pation due to lack of
visual information
Gazing at an in-
vehicle display or
- Sensory conflict by
inconsistency be-
tween the passen-
gers body movement
and what they see
- Decrease of antici-
pation due to ab-
sence of visual in-
formation from the
road environment
Changes in
the vehi-
cle sys-
caused by
the auto-
control of
the vehi-
Changes in
vehicle mo-
Driving velocity pat-
tern in curves
- Vehicle motion af-
fects motion sick-
Changes in in-
Changes in the size
of the front window
- Narrowing front
visual image
- Decrease in antici-
pation of the vehicle
2.1 Changes for drivers: Transformed into
(a) Motion sickness susceptibility difference be-
tween driver and passenger
Rolnick & Lubow (1991) reviewed the factors con-
tributing to motion sickness that differ between
drivers and passengers, namely, controllability, per-
ceived control, activity, visual information, and pre-
dictability. The perceived control represents whether
the driver feels he/she is in control of the vehicle;
thus, it is thought to be identical to sense of agency
(David et al. 2008). In a real-world automotive envi-
ronment, the controllability and perceived control
are identical. It is thought that increasing these fac-
tors reduces motion sickness (Reason 1978b). In the
automated driving, the drivers are relieved of the
control operation and become a passenger; thus, the
susceptibility to motion sickness can be increased
(Rolnick & Lubow 1991)(Reason 1978b). Activity
is difficult to quantify. It has been reported that the
effect of an activity on a person’s motion sickness
susceptibility depends on the type of activity being
performed. A driving-related activity might reduce
motion sickness, but a non-driving-related activity
can increase it. The ability to predict future motion
is thought to differ between the driver and passen-
gers: a passenger’s predictability might be reduced
because they do not need to control the vehicle’s
motion. Regarding visual information, the visual
field or other optical input to the eyes affects motion
sickness. In addition, visual information is also
strongly related to predictability. If the occupants
could change their seating position or direction such
as by facing toward the rear, this could affect their
visual information and predictability. These points
were discussed in Diels & Bos (2015) and Sivak &
Schoettle (2015).
In addition, the driver is known to tilt his or her
head toward the center of the curve when negotiat-
ing a curve, whereas a passenger's head moves in the
opposite direction Wada et al. (2012). Wada et al.
(2012) and Wada & Yoshida (2015) revealed that if
a passenger tilts their head against the centrifugal
force in slalom driving, in imitation of the driver’s
head movement, it significantly reduces the severity
of motion sickness compared with tilting their head
toward the centrifugal force. This indicated that head
tilt affects the susceptibility to motion sickness.
(b) Increase of non-driving tasks
Being relieved of the driving operation increases an
occupant’s ability to use a tablet, watch a handheld
display, or engage in other non-driving activities.
Because the occupant is not required to monitor the
road in theory, he/she can look at the visual display
for a long time. Inconsistency between a passenger’s
body movement and what they see can increase mo-
tion sickness (Reason 1978a). A decrease in antici-
pation of body movement as a result of looking at a
display is also thought to be a risk factor.
2.2 Changes in vehicle system: Driving operation
replaced by automation
No study could be found that investigated from the
viewpoint of changes in vehicle system or driving
operation being replaced by automation. It is possi-
ble to dramatically change the motion pattern or ve-
locity profile of an automated vehicle. A human
driver is thought to drive in a manner that prevents
motion sickness even without passengers because a
driver that does not want to get carsick functions as
a type of motion sickness detector or predictor. On
the other hand, to design the motion pattern for an
automated vehicle with a view to minimizing motion
sickness, it is necessary to quantitatively evaluate
the motion sickness severity for a given vehicle mo-
tion. Section 3 will introduce a mathematical model
of motion sickness to estimate its incidence.
In addition, because no human controls the vehi-
cle motion, the size and shape of the windows can be
changed. Employing smaller windows may increase
passengers’ susceptibility to motion sickness be-
cause of reductions in the visual field and the ability
to predict future movements (Griffin & Newman
2004). The effect could include the decrease in an-
ticipation of body motion due to lack of visual in-
formation in front.
As a method to quantify severity of motion sick-
ness, the motion sickness dose value (MSDV) is
used, which is the integration of frequency-weighted
acceleration (McCauley et al. 1976)(Kato & Kita-
zaki 2006). On the other hand, Bles et al. (1998)
proposed the subjective vertical conflict (SVC) theo-
ry, which postulates that motion sickness is caused
by the accumulation of conflict between the vertical
direction of the body sensed by the sensory organs
and the predicted motion by an internal model that is
thought to be established in the central nervous sys-
tem. A mathematical model for the SVC theory was
proposed, detailed for one degree-of-freedom (DOF)
motion (Bos & Bles 1998). We propose the 6DOF-
SVC model (Fig.1), which predicts motion sickness
incidence (MSI) in 6 DOF motion in 3D space as an
extension of the Bos & Bles (1998) model by intro-
ducing semi-circular canal and canal-otolith interac-
Please refer to Wada, Fujisawa, et al. (2010) for the
detail of the mathematical model.
Internal model
Sensory organs
Head Acc.Gravity + Inertial accel.)
Angular velo.
Head accel.
Internal model
Figure 1. Mathematical model of motion sickness
(Wada, Fujisawa, et al. 2010).
4.1 Vehicle control
4.1.1 Design of vehicle motion minimizing motion
As mentioned before, it is necessary to consider
motion sickness explicitly in designing vehicle mo-
tion of an automated vehicle. Given the mathemati-
cal model of motion sickness, the vehicle control
that minimizes the MSI can be designed. In this sec-
tion, a vehicle motion generation method that mini-
mizes the predicted MSI by the 6DOF-SVC model is
introduced (Wada et al. 2015).
(a) Road geometry
Consider single lane roads with curves where a
driver should decelerate to an appropriate velocity
before and/or during negotiating a curve, and then
accelerate again when returning to a straight if nec-
essary. Suppose that road geometry is given by a
plane algebraic curve. For the sake of simplicity, as-
sume that both ends of a curve with a constant cur-
vature are connected to a straight via clothoid curves
(Fig.2). Let parameter s be an arc length at a point
measured from a given origin; then, the road geome-
try can be described by specifying
(s), which is the
angle of tangent line at s measured from the x-axis
of the road-fixed Cartesian coordinate system o-xy
Figure 2. Description of road geometry (Wada et al. 2015).
(b) Vehicle control method
The deceleration control method that was derived
from expert drivers’ deceleration profile (Wada,
Doi, et al. 2010) is expanded to accelera-
tion/deceleration control here.
In a single block of road, including a curve defined
as 0][,
s, as shown in Fig.1, velocity patterns in
which it is assumed that a vehicle drives at a con-
stant velocity, decelerates to a certain velocity,
drives at the constant velocity, accelerates to a given
velocity, and drives at the velocity, are formulated as
01 1
012 1 2
23 2
00 0
14 4
() := ( ) (1)
( )
( )
ff f
s,s s
f v ,v ,s ,s s
v s f v ,v ,s ,s s
f v ,v ,s ,s s
f v ,v ,s ,s sss
:=v ( )exp{3(1- ( )},
() := (3
ji l kl
f v ,v ,s ,s
v,s ,sv)d s,s ds,s
ds,s ,
where vo, vf denote the velocity at s=s0 and sf, re-
spectively, and va denotes the velocity at the con-
stant velocity that is expected to appear in the curve.
Scalars s1 and s2 are the start and end positions of
the deceleration, and s3 and s4 are the start and end
positions of the acceleration. Assuming that the oc-
cupant’s head moves in accordance with the vehicle
motion, the head acceleration and the angular veloci-
ty are determined by specifying the vehicle velocity
on the road; thus, the predicted MSI is calculated us-
ing the 6DOF-SVC model. Therefore, the design of
the velocity pattern can be formulated by following.
[Design of velocity profile]
Given: 0,,()
( 0][,
Find 1234
which minimizes MSI calculated using 6DOF-
SVC model.
s.t. 1234
00, 0, 0
vv v
where t0 and tf are the times when the vehicle is at s
= s0 and s = sf, respectively.
This problem can be solved by employing appropri-
ate nonlinear optimization method such as Neldar-
Mead Simplex Method.
(c) Results
Fig.3 shows the generated velocity profile for a road
course designed to be driven at 20 km/h following
the Road Construction Ordinance of the Ministry of
Land, Infrastructure, Transport and Tourism in Ja-
pan, in which 010m/s
vv was set. Driving time, T,
was changed as 10 through 60 s. The velocity pro-
files in which the vehicle decelerated before entering
the curve, drive at a constant speed, and accelerate
again were successfully generated, and they con-
firmed our prediction.
4.2 Behaviors
An occupant’s behavior affects motion sickness.
The seating posture can be modified to reduce mo-
tion sickness because it is known that sleeping and a
supine posture reduce motion sickness (Diels & Bos
2015)(Sivak & Schoettle 2015). Thus, the location
and direction of the seats should be considered care-
In addition, from Wada et al. (2012)and Wada &
Yoshida (2015), tilting the head angle toward the
center of a curve reduces motion sickness. However,
it should be noted that passive head movement
might conversely increase motion sickness because
motion sickness increases in a tilt train (Persson
2008). Thus, a method to encourage such a head tilt
naturally is needed to facilitate this. For this pur-
pose, we proposed a postural control device using
pneumatic balloon installed on the drivers’ seat that
encourages drivers’ head tilt towards centripetal ac-
celeration when negotiating a curve (Konno et al.
4.3 User interfaces
The chances that the occupants use a tablet or other
devices can be increased while riding in automated
vehicles. The display design of such devices plays a
Figure 3. Generated velocity profile(Wada et al. 2015).
crucial role in decreasing motion sickness. In Diels
& Bos (2015), a design guideline for such user inter-
faces is provided, but it is omitted here owing to
lack of space.
There is a possibility to add visual information to
provide road geometry ahead, etc., to increase the
anticipation to reduce motion sickness. For this, ef-
fort in software to reduce motion sickness is possi-
ble. For example, Morimoto et al. (2008) successful-
ly reduced motion sickness while watching a video
in a passenger car by deforming a video image that
was played on an in-vehicle monitor.
This paper discussed factors related to motion
sickness in automated vehicles from the viewpoint
of changes for drivers caused by being relieved from
the driving operation and those in the vehicle system
controlled by the automation. Considering the im-
portance of quantifying motion sickness, a mathe-
matical model of motion sickness was introduced
with the goal of providing countermeasures. Finally,
some countermeasures were proposed from the
viewpoints of vehicle control, behavior, and a user
interface, which put an emphasis on a vehicle con-
trol method to minimize MSI.
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... However, the motion that causes nausea and other physical discomfort to passengers is relatively ignored. Wada [3] proposed a countermeasure to minimize motion sickness by designing velocity profile of self-driving vehicles on a fixed road with different straight and curve regions. From our knowledge, there are examples of motion planning for tilted train [25] and high-speed rail [26]. ...
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... Technically, a longitudinal control system or speed control system is used to control the acceleration and the deceleration of the vehicle. Wada et al. presented a velocity profile based on the expert driver's profile to be installed in the autonomous vehicle to reduce MS [51]. During curvature, the vehicle's speed will be lowered to achieve low lateral acceleration. ...
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... The longitudinal vehicle dynamic can be modulated by the adaptive cruise control (ACC) or prospectively the AV longitudinal control [15] in order to influence carsickness. Alternatively, decoupling certain parts of a vehicle can smoothen vibration transmission from the road to the passenger. ...
Conference Paper
The problem of motion sickness in cars is receiving increased attention due to the development of automated driving functions. This evolution of driving provokes changes in the role of the driver and non-driving activities become more relevant for all passengers. The full control of the driving dynamics enables car manufacturers to influence stimulations that provoke motion sickness. In parallel, passenger activities like video watching increase the probability of symptoms for individuals that are susceptible to motion sickness. Based on those circumstances,technical solutions that allow user experiences without motion sickness need to be developed.The movement perception by the associated organs of balance and the eyes plays a key role in the conflict of motion sickness. This investigation evaluated two concepts that address the human vestibular and visual systems in order to reduce motion sickness. The effects of a prototypical decoupled seat and a virtual animation of the vehicle environment were compared to a reference condition. The experimental environment consisted of a naturalistic reproduction of stop-and-go-driving on theproving ground. The participant’s task was to watch a video while being driven. Meanwhile, symptoms of carsickness were retrieved and objective parameters of head and eye movement recorded. The study results do not show significant improvements on carsickness due to the realized concepts. Furthermore, the selected parameters for monitoring behavioral patterns of the head and eye movement were unaffected as well. Consequently, a review of the concept principles as well as an advancement of the physical prototypes are needed.
... There is a demand for early detection of motion sickness in engineering, which can be seen with recent advances in highly automated driving systems (Wada, 2016). However, the dynamics of symptom or severity of motion sickness has a large time constant. ...
The vestibulo-ocular reflex (VOR) is the reflexive eye movement occurring in the opposite direction of head movement to stabilize the visual image during head movement. We hypothesize that there exists a correlation between motion sickness and the accuracy of VOR because motion sickness and VOR are thought to be related to the head movement signals estimated in the central nervous system. The first purpose of the present research is to investigate the relationship between motion sickness and VOR accuracy using a mathematical model, which simultaneously describes motion sickness and VOR. The result of numerical simulation experiments shows a strong negative correlation between VOR accuracy and the severity of motion sickness. The second purpose is to investigate the relationship between motion sickness and VOR accuracy by experiments on humans. The result shows moderate negative correlations between the VOR accuracy and the severity of motion sickness among participants.
... In addition to acceptance and comfort frequently mentioned in Table 1, the holistic driving experience should be considered in the process of developing automated driving styles. In particular, aspects resulting from the automation of the dynamic driving task, such as performance of non-driving related tasks and associated motion sickness [69], should not be neglected. To meet as many individual customer requirements as possible, we recommend, along with other researchers (e.g., [16,35,39,70]), to offer options to individualize the automated vehicle behavior and thus to implement diverse automated driving styles in automated vehicles (see three colored areas in Figure 3). ...
In the human-centered research on automated driving, it is common practice to describe the vehicle behavior by means of terms and definitions related to non-automated driving. However, some of these definitions are not suitable for this purpose. This paper presents an ontology for automated vehicle behavior which takes into account a large number of existing definitions and previous studies. This ontology is characterized by an applicability for various levels of automated driving and a clear conceptual distinction between characteristics of vehicle occupants, the automation system, and the conventional characteristics of a vehicle. In this context, the terms ‘driveability’, ‘driving behavior’, ‘driving experience’, and especially ‘driving style’, which are commonly associated with non-automated driving, play an important role. In order to clarify the relationships between these terms, the ontology is integrated into a driver-vehicle system. Finally, the ontology developed here is used to derive recommendations for the future design of automated driving styles and in general for further human-centered research on automated driving.
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There are concerns that viewing two-dimensional (2D) content such as web pages on a head-mounted display (HMD) in the car may aggravate motion sickness. This is because when 2D content is fixed to a head-fixed coordinate system, the appearance of the content does not change even when the body moves; therefore, it is impossible to visually perceive the movement of one’s body, resulting in a sensory conflict between the visual and vestibular senses. A method for reducing motion sickness when displaying 3D content on an HMD has been investigated; however, when displaying 2D content, no such method has been investigated. Therefore, this study aims to verify to the possibility of reducing motion sickness from the change of appearance caused by fixing 2D content to the earth-fixed coordinate system when viewing it with an HMD in a moving environment. Participants sat on a seat that was mounted on a vibrating device and moved in the pitch direction while reading a book on the HMD. Consequently, the severity of motion sickness was significantly lower when the book was fixed to the earth-fixed coordinate system than when fixed to the head-fixed coordinate system. This result suggests that by fixing the content to the earth-fixed coordinate system, motion sickness can be reduced because the movement of one’s body can be perceived through changes in the appearance of the content, and the sensory conflict between visual and vestibular sensations can be resolved.
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Two hypotheses based on the sensory conflict theory were postulated as possible means for reducing carsickness: (1) Reducing signals from the vestibular and vision systems through a reduction of low-frequency motion would mitigate carsickness and (2) Controlling stimulation of visual organs so as to reduce the amount of sensory conflict would mitigate carsickness. For hypothesis (1), the relations between subjective carsickness ratings and motions of the vehicle and passengers' body were investigated. Greater correlation was found between carsickness ratings and motions of the passengers' head, where the organs of the vestibular and vision systems are located, than between carsickness ratings and vehicle motions. For hypothesis (2), the incidence of carsickness in passengers who gazed at an in-vehicle display was investigated because there seemed to be large conflict between the vestibular system and the vision system. It was found that modification of the visual information presented on the display in a way that did not conflict with signals from the vestibular system reduced carsickness.
Conference Paper
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Car drivers receive the acceleration stimulation and the rotational stimulation when negotiating with a curve. In such a situation, the driver controls his/her posture such as the head and the body appropriately. It is known that the driver tilts his/her head toward the curve direction while the passengers' head movement is likely to occur in the opposite direction. There are some interpretations of the role of the driver's active head movement such as increasing visibility and decreasing of effect of the inertial force to the body including the trunk and the neck. The goals of this research are to understand relationship between head tilt strategy and motion sickness incidence and apply its result to the design of comfortable vehicle motion. First, we derive a mathematical model of the motion sickness incidence caused by the head movement in 3D space based on subjective vertical conflict. Then, we analyze effect of the head movement on decrease of motion sickness incidence using the mathematical model.
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This study examined the effect of passengers’ active head-tilt and eyes-open/eyes-closed conditions on the severity of motion sickness in the lateral acceleration environment of cars. In the centrifugal head-tilt condition, participants intentionally tilted their heads towards the centrifugal force, whereas in the centripetal head-tilt condition, the participants tilted their heads against the centrifugal acceleration. The eyes-open and eyes-closed cases were investigated for each head-tilt condition. In the experimental runs, the sickness rating in the centripetal head-tilt condition was significantly lower than that in the centrifugal head-tilt condition. Moreover, the sickness rating in the eyes-open condition was significantly lower than that in the eyes-closed condition. The results suggest that an active head-tilt motion against the centrifugal acceleration reduces the severity of motion sickness both in the eyes-open and eyes-closed conditions. They also demonstrate that the eyes-open condition significantly reduces the motion sickness even when the head-tilt strategy is used. Practitioner Summary: Little is known about the effect of head-tilt strategies on motion sickness. This study investigated the effects of head-tilt direction and eyes-open/eyes-closed conditions on motion sickness during slalom automobile driving. Passengers’ active head tilt towards the centripetal direction and the eyes-open condition greatly reduce the severity of motion sickness.
Technical Report
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The purpose of this study was to investigate user interactions with Level 2 and Level 3 partially automated vehicles. L2 and L3 were of interest because it is at this point where the driver’s role transitions and longitudinal and lateral control are ceded in varying degrees to the vehicle. At this point, the driver becomes an intermittent operator. For L2 and L3, the level of involvement by the human might vary. Therefore, we use the term operator as opposed to driver. The study focused on how these intermittent operators transition between automated and non-automated vehicle operation, and how this interaction is affected by the human-machine interface (HMI). Three experiments were performed with prototype partially automated vehicles on controlled test tracks in mixed traffic. The first experiment investigated which HMI characteristics are most effective at issuing a take-over request (TOR) during the operation of an L2 automated vehicle. The second experiment investigated how to prompt operators to attend to the road when distracted during the operation of an L2 automated vehicle, and whether these prompts are effective over time. The third experiment investigated which HMI characteristics are most effective at issuing a TOR during the operation of an L3 automated vehicle. The findings suggest that the most effective hand-off strategies were those that incorporated nonvisual components. The driver engagement patterns observed in this study provide data and evidence that could support the future development of human factors design principles for L2 and L3 partially automated vehicles.
Conference Paper
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Self-driving cars have the potential to bring significant benefits to drivers and society at large. However, all envisaged scenarios are predicted to increase the risk of motion sickness. This will negatively affect user acceptance and uptake and hence negate the benefits of this technology. Here we discuss the impact of the user interface design in particular, focusing on display size, position, and content and the relationship with the degree of sensory conflict and ability to anticipate the future motion trajectory of the vehicle, two key determinants of motion sickness in general. Following initial design recommendations, we provide a research agenda to accelerate our understanding of self-driving cars in the context of the scenarios currently proposed. We conclude that basic perceptual mechanisms need to be considered in the design process whereby self-driving cars cannot simply be thought of as living rooms, offices, or entertainment venues on wheels.
Conference Paper
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This driving simulator study, conducted as part of the EC-funded AdaptIVe project, investigated the effect of level of distraction during automation (Level 2 SAE) on drivers' ability to assess automation uncertainty and react to a potential collision scenario. Drivers' attention to the road was varied during automation in one of two driving screen manipulation conditions: occlusion by light fog and occlusion by heavy fog. Vehicle-based measures, drivers' eye movements and response profiles to events after an automation uncertainty period were measured during a highly automated drive containing one of these manipulations, and compared to manual driving. In two of seven uncertainty events, a lead vehicle braked causing a critical situation. Drivers' reactions to these critical events were compared in a between-subjects design, where the driving scene was occluded for 1.5 minutes. Results showed that, during automation, drivers were less engaged their response profile to a potential collision scenario was less controlled and more aggressive immediately after the transition, compared to when they were in manual control. During the automated drive, drivers in heavy fog condition collided with the lead vehicle more and also had a lower minimum headway compared to those in light fog.
Conference Paper
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Driver tilts his/her head to the direction of the curve center. Beside, it is pointed out that the head movement of the passenger is opposite to the driver. Moreover, it is known that the driver does not get carsickness comparing with the passenger. Therefore, we investigate the effect of the driver's active head movement. We build the mathematical model of the motion sickness and simulate the severity of motion sickness using driver's head movements measured in the real-car experiments. From the result, it is shown that the driver's head movement has an effect to decrease the motion sickness. Then we proposed a novel posture control device based on the results. It is shown that the developed device changes the passengers head tilt toward the driver's direction, which can decrease the motion sickness.
Onboard displays are becoming popular as rear-seat entertainment in vehicles. However, watching video displays frequently causes car sickness in the same way as reading books in a moving vehicle. We propose two approaches to reduce car sickness while watching an onboard display. An experimental study showed that car sickness was markedly reduced by applying our proposed approaches.
Conference Paper
Car drivers receive the acceleration stimulation and the rotational stimulation when negotiating with a curve. In such a situation, the driver controls his/her posture such as the head and the body appropriately. It is known that the driver tilts his/her head toward the curve direction while the passengers' head movement is likely to occur in the opposite direction. There are some interpretations of the role of the driver's active head movement such as increasing visibility and decreasing of effect of the inertial force to the body including the trunk and the neck. The goals of this research are to understand relationship between head tilt strategy and motion sickness incidence and apply its result to the design of comfortable vehicle motion. First, we derive a mathematical model of the motion sickness incidence caused by the head movement in 3D space based on subjective vertical conflict. Then, we analyze effect of the head movement on decrease of motion sickness incidence using the mathematical model.