Will autonomous vehicles make us sick?

Abstract

Autonomous vehicles have the potential to radically change the way we use and interact with our cars. Current thinking assumes that drivers will engage in non-driving tasks and, accordingly, future vehicle design may look dramatically different. However, the use cases envisaged are also known to exacerbate the incidence and severity of carsickness. This paper will discuss these scenarios with reference to the aetiology of carsickness and suggest design constraints to facilitate acceptable future autonomous vehicle design.

Full text

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
301
WILL AUTONOMOUS VEHICLES MAKE US SICK?
Cyriel Diels
Coventry School of Art & Design, Department of Industrial Design, Coventry
University, Priory Street
Coventry CV15FB, UK
Cyriel.Diels@coventry.ac.uk
Autonomous vehicles have the potential to radically change the
way we use and interact with our cars. Current thinking assumes
that drivers will engage in non-driving tasks and, accordingly,
future vehicle design may look dramatically different. However,
the use cases envisaged are also known to exacerbate the incidence
and severity of carsickness. This paper will discuss these scenarios
with reference to the aetiology of carsickness and suggest design
constraints to facilitate acceptable future autonomous vehicle
design.
Introduction
Maturation, integration and affordability of enabling technologies have turned
automated driving into a reality. We have seen Google’s driverless car clocking
up thousands of accident-free miles and now several US states, the UK and Japan
have passed laws permitting (human-supervised) autonomous cars on their roads
for R&D purposes. Several car manufacturers including GM, Mercedes, and
Nissan, also recently announced their intention to offer semi-autonomous
vehicles by 2020. These vehicles provide dual-mode operation whereby, on
demand, longitudinal and lateral vehicle control can be handed over to the
vehicle. The system essentially combines full range adaptive cruise control with
automated lane keeping applying steering actions using electrical power steering.
On-road trials are currently also underway to evaluate so-called platoon driving,
i.e. the grouping of vehicles maintaining a short time headway achieved by using
a combination of wireless communications, lateral and longitudinal control units,
and sensor technology. Current concepts under consideration assume a system
whereby the platoon is led by a trained, professional driver whilst the following
vehicles are driven fully automatically by the system (for an overview of vehicle
automation see SMART 2011).
By taking the driver out of the loop, automated personal mobility has the
potential to be more efficient, safer, and greener (e.g. Robinson et al. 2010). At
the same time, it allows drivers to engage in non-driving tasks. With vehicle
control in the hands of the automated system, the driver, now passenger, can sit
back and relax, have a coffee, check emails, read the morning paper, or swivel
his or her chair and have a face to face conversation with other passengers.

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
302
Vehicle interiors will be designed to become more like social, work, and
entertainment spaces.
Besides the critical aspect of liability, there are several human factors issues that
require a better understanding to ensure the successful introduction of vehicle
automation. Current research activities focus around the topics of transfer of
control, situational awareness, HMI design, mixed traffic conditions, system
trust, reliability, and user acceptance. There is one aspect, however, that thus far
has appeared to have gone unnoticed: carsickness.
Susceptibility to carsickness varies widely but it has been found that around 60%
of the population has experienced some nausea from car travel, whereas about a
third has vomited in cars before the age of 12 (Griffin, 1990). Although the
ultimate manifestation of motions sickness is vomiting, it is typically preceded
by signs and symptoms such as nausea, headache, fatigue, and drowsiness which
may linger on for hours (Griffin, 1990).
Coincidentally, the use cases that are being envisaged for automated driving are
also those we know to lead to increased levels of carsickness. First, automation
alters the driver’s function from an active to a passive, monitoring one.
Secondly, occupants are assumed to engage in non-driving tasks taking the eyes
off the road ahead. Finally, flexible seating arrangements may involve rearward
facing seats. In the context of carsickness, the common denominator across
above scenarios or use cases is the occupants’ inability to sufficiently accurately
predict the future path of the vehicle which is known to be a main determinant of
sickness (e.g. Golding & Gresty, 2013). Following a brief introduction to the
aetiology of carsickness, the different use cases and their exacerbating effect on
carsickness will be discussed below.
Aetiology of carsickness
Motion is primarily sensed by the organs of balance located in the inner ear and
our eyes. Motion sickness can occur when these motion signals are in conflict
with one another or when we are exposed to motion that we are not accustomed
to (Reason, 1975; Oman, 1982). It can be caused by a wide variety of motions of
the body and the visual scene and is a common problem in travellers by car,
train, air, and particularly sea. Seasickness may happen whilst being below deck
where a clear view of the visual scene outside the ship is lacking. Under these
conditions, motion sickness occurs because the movements of the ship, as
perceived by the organs of balance, are in conflict with the motion perceived by
the eyes, which indicate a static visual surround.
Sickness can however also occur when we are exposed to motion that, from an
evolutionary perspective, we are not used to. Our bodies are not accustomed to
low frequency oscillating motion. Sea and airsickness, for example, are mainly
caused by slowly oscillating vertical motion. Carsickness, on the other hand, is

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
303
associated with horizontal accelerations (sway) caused by acceleration, braking,
and cornering (Guignard & McCauley, 1990; Turner & Griffin, 1999).
With regard to carsickness, it is linear accelerations (sway) in the low frequency
bands (0.1-0.5 Hz) that are most relevant and their effects increase as a function
of duration of exposure and the intensity of acceleration (Turner & Griffin,
1999). Apart from the route itself, carsickness heavily depends on the way the
car is driven. An aggressive driving style involving plenty of accelerating and
braking is therefore more likely to result in carsickness. A study on suburban car
journeys reported that the fore-and-aft and lateral acceleration motion patterns
were similar over the lower frequency range and were provocative in inducing
motion sickness. These low frequency fore-and aft and lateral oscillations are
more dependent on the driving behaviour of the driver than the characteristics of
the vehicle (Griffin & Newman, 2004).
Characteristics of the vehicle mainly affect higher frequency motion. Similarly,
road surface quality also affects the high frequency motion vibrations. From this
it follows that road surface quality and suspension affect riding comfort, but do
not induce carsickness. Exceptions to this rule are cars with particular soft
suspensions. In general, when the suspension frequency is below 1 Hz, the
likelihood of carsickness significantly increases (Turner & Griffin, 1999). Cars
with stiffer suspensions are therefore less likely to lead to cars sickness. Larger
amplitudes of lateral (sway) are particularly provocative. As the amplitude of
sway tends to increase towards the rear of vehicles (cars and buses), rear seat
passengers are particularly prone to car sickness, especially under conditions
where external visual views are limited (Turner & Griffin, 1999).
Carsickness and Autonomous Vehicles
The novel use cases that are being envisaged for autonomous driving are also
those we know to significantly increase the incidence and severity of carsickness.
First, automation alters the driver’s function from an active to a passive,
monitoring one. Secondly, occupants are assumed to engage in non-driving tasks
taking the eyes off the road ahead. Finally, flexible seating arrangements may
involve rearward facing seats. In the context of carsickness, the common
denominator across above scenarios is the occupants’ inability to sufficiently
accurate predict the future path of the vehicle which is known to be a main
determinant of sickness (e.g. Golding & Gresty, 2013).
Changing roles: From driver to passenger
With longitudinal and lateral vehicle control automated, the driver is no longer
required to actively engage in the driving task. In dual-mode systems where the
driver has the choice to drive the vehicle manually or hand over control to the
automated system, the driver may still be required to monitor vehicle status to
allow for manual override in case of emergencies. In effect, however, the driver
becomes a passive passenger.

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
304
It is commonly reported that drivers of cars, pilots of aircraft, or Virtual Reality
users in control of their own movements are usually not susceptible to motion
sickness despite the fact that they experience the same motion as their passengers
(Geeze & Pierson, 1986; Reason & Brand, 1975; Stanney & Hash, 1998). This
moderating effect of control on the generation of motion sickness symptoms has
typically been attributed to the presence of muscular activity. When we initiate a
movement, a copy of the movement command sent out by our central nervous
system (CNS), referred to as an “efference copy”, is used to perform a simulation
of the expected results (output or “reafference”) of the command. The expected
reafference is then compared with the actual sensed reafference within an
internal model in our CNS. If there is a discrepancy, for example, a movement
command normally used to move our finger to our nose does not produce the
intended arm movement due to additional exercise weights added to the wrists,
the internal model is updated. In this case, the efferent signal is increased to
account for the increased resistance. Taking the weights off subsequently results
in arm overshoot and thus requires a further recalibration of the internal model.
The presence of an efference copy to activate an internal model is thought to
facilitate this habituation process. With reference to motion sickness, those in
control can benefit from this mechanism to a larger extent and are generally
found to desensitise or habituate much faster (Oman, 1982; Reason, 1978;
Reason & Benson, 1978; Reason & Brand, 1975; Rolnick & Lubow, 1991; Stott,
1990). Oman (1991) argued that motion stimuli are relatively benign when
individuals are able to motorically anticipate incoming sensory cues. However, a
fundamental question is whether this anticipatory mechanism is only activated
when the perturbation is self-produced or whether this mechanism is also set in
motion in case the perturbation is made predictable by sensory information.
An anticipatory mechanism has been explicitly incorporated in the Subjective
Vertical-conflict model or SV-conflict model developed by Bles and colleagues
(Bles et al., 1998). As in the classical sensory conflict theory (Oman, 1982;
Reason, 1978), self-initiated movement results in an efference copy of the
command signal sent to the internal model which subsequently predicts how the
body will react, what the sensor responses will be, and which motion and body
attitude is to be expected. In the SV-conflict model, however, an anticipatory
mechanism is incorporated so that even during imposed passive motion, the
internal model is also activated as long as this motion can be anticipated based
on sensory information. Therefore, the SV-conflict model predicts that not only
drivers but also passengers sitting next to the driver to be less prone to motion
sickness, provided passengers have a clear view and looking at the road ahead
(Bles et al., 1998; Bles et al., 2000). Note, however, that this does not preclude
particularly sensitive passengers from getting sick.
Engagement in non-driving activities
Automated vehicles allow the driver to engage in non-driving activities. It is
highly probable that popular activities may include reading, checking one’s
emails, or engaging otherwise with nomadic or integrated infotainment systems
such as in-vehicle displays, laptops, video games, or tablets. On the basis of the

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
305
sensory conflict theory of motion sickness, one would expect to see an increase
in carsickness under these conditions. Similar to reading a map or book whilst
driving, the (static or dynamic) image displayed on displays will not correspond
to the motion of the vehicle which ultimately may lead to carsickness. This will
be particularly true for downward viewing angles or displays that prevent a clear
view from the road ahead or horizon. Note therefore that see-through displays
may provide one possible solution to minimise the impact of incongruent motion
cues.
Research indicates that in-vehicle entertainment systems indeed increase the
likelihood of carsickness. Cowings et al. (1999) reported a negative impact on
crew performance and health when subjects attended to visual computer screens
while the vehicle was moving. More recently, in a study by Kato and Kitazaki
(2008), 20 people were driven around for 30 minutes whilst sitting in the
backseat either watching the road ahead, or a rear-seat display showing written
text. During each of the two drives, the participants were asked to verbally rate
their motion sickness on a motion sickness scale that ranged from 0 (“No
symptoms, I feel fine”) to 6 (“moderate nausea, I want to stop”). As expected
based on the conflict between the motion sensed by the visual and vestibular
system, results confirmed that watching the in-car screen led to significantly
higher levels of carsickness.
Flexible seating arrangements
An idea that can be traced back to at least the 50’s, autonomous vehicles are
considered to provide an opportunity to facilitate social interaction. Numerous
concepts for autonomous vehicles suggest flexible interior layouts which
frequently involve swivelling chairs allowing the driver and front passenger to
turn to the rear passengers. In the light of the previous sections, it becomes
apparent that facing rearwards may not only lead to conflicting sensory
information provided by the visual and vestibular system, it also reduces the
ability to anticipate the future motion path. Consequently, alternative layouts
with rearward facing seats will almost certainly lead to increased levels of
carsickness.
Surprisingly, there appears to be no published data to support this contention
however. This is even more surprising given the fact that rearward facing seats
are standard in trains. UK train operators offer customers the option to choose
the preferred direction of travel when purchasing pre-booked tickets. This would
imply a significant proportion of the customer base to have a preference to travel
forward facing. This is in agreement with the anecdotal evidence which suggests
that passengers prefer not to face rearwards in order to avoid motion sickness.
Facing forwards allows the passenger to anticipate the train’s motion to a large
extent than facing backwards even though the available visual information in
trains will be limited. Unlike drivers, train passenger will not be able to see the
Focus Of Expansion (FOE) which refers to the most informative part of the
observers’ visual field with regard to the direction of travel.

Diels, C. (2014). Will autonomous vehicles make us sick? In S. Sharples & S. Shorrock (Eds.),
Contemporary Ergonomics and Human Factors (pp. 301-307). Boca Raton, FL: CRC Press.
306
Design Implications for Autonomous Vehicles
The above discussion points towards 2 fundamental principles that need to be
taken into account to prevent carsickness: (1) avoid sensory conflict where
possible, and (2) maximise the ability to anticipate the future motion path. When
applied to the design of autonomous vehicles and its anticipated use cases, the
following design guidelines are suggested.
Forward and sideway visibility should be maximised. Ideally occupants have a
clear view of the road ahead. However, under conditions that this view is
compromised, any visual information (i.e. optic flow) that correctly indicates the
direction of travel will reduce the amount of sensory conflict and enhance the
ability to anticipate the motion path. The design should therefore aim for
maximum window surface areas or Day Light Openings (DLO), minimal
obstruction by A-, B-, and C-pillars, and low belt lines or seats of sufficient
height to ensure passengers ability to look out of the vehicle. New lighting
technologies such as OLED (Organic Light Emitting Diodes) may provide the
possibility to provide simulated optic flow patterns inside the vehicle. See-
through displays, such as head up displays will reduce the impact of incongruent
motion cues. Future research may also explore the effectiveness of using visual,
auditory, and/or tactile cues to provide an artificial horizon and signal the future
motion path. With regards to seasickness and airsickness, artificial spatial or
motion cues have already been shown to alleviate sickness (e.g. Rolnick & Bles,
1989; Tal et al. 2012). The extent to which these techniques can be extrapolated
to the automotive field has yet to be determined.
Finally, the occurrence of carsickness in autonomous vehicles will be dependent
on the driving scenario. Our organs of balance are in essence biological
accelerometers and this means that they are sensitive to accelerations only
(Howard, 1982). As a corollary, sensory conflict and hence the likelihood
carsickness from occurring, is significantly reduced when traveling at constant
speed. The organs of balance signal the body to be stationary and therefore any
stationary scene as sensed by our eyes will be perceived as congruent. Under
conditions of constant motion, i.e. no lateral or longitudinal accelerations,
carsickness is less likely to occur. With respect to the implementation of
autonomous systems this would suggest that future levels of carsickness may be
manageable provided the automation is not applied under traffic conditions that
involve high levels of accelerations as typically observed in urban or rush hour
motorway traffic.
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