This video presents Queasy Rider: How Head Movements Influence Motion
Sickness in Passenger Use of Head-Mounted Displays. This work is conducted by me,
Hi everyone, I am Jingyi Li.
together with Agnes Reda and Andreas Butz from LMU Munich Media Informatics Group.
In self-driving cars, the driver will spend more time on non-driving-related
activities. Similar to a rear-seat passenger today, the driver can use multiple mounted
displays or even mobile head-mounted displays in virtual reality to have a video call on the way.
A wider head motion range can increase engagement in such activities, but might also amplify the
risk of motion sickness while switching between displays. Therefore, we aim to quantify optimal
head movements for a good trade-off between motion-sickness and the feeling of engagement in passenger activities.
We designed a head-gaze-based dwell-time interaction in VR HMD
along the horizontal and vertical axis. Based on the frequency of 0.2 Hz tested in prior work,
we investigated three head motion ranges: 25 degrees , 50 degrees, and 65 degrees with their calculated speeds,
two orientations: pitch and yaw axis, and three durations of dwell-time: 0.3s, 1s, and 3s
Here is an example of a passenger performing the 50-degree head movement, along the Y and the X-axis, using 1s dwell time to hit the red targets.
In Unity, we implemented a virtual display with a cross shape
located at a distance of 2.05 m. The display shows the content of a moving low-poly bird to guide the
passenger s head movement and a hover area with an identical size of the red square target.
We chose a 4.4 km city highway with relatively controlled traffic conditions and a good road
quality. The main test route was an almost straight road for about 5 minutes of driving.
The experimenter controlled the driving style with a constant speed of 80 km/h in a Toyota Yaris
Hybrid and performed no stops in between. For the HMD task, we used the Oculus Quest,
a consumer-grade standalone VR headset. We tracked passenger head movements via the headset.
We mapped the left-hand controller to the real-time car movements and synchronously subtracted it from the rotation of the VR Headset.
We planned this study using a within-subject design.
In total, we invited 21 participants to the study. 12 men and 9 women with a mean age of 27.4 years
and a mean MSSQ raw score of 12.6. Most of them, like 17 people, had no or rare prior
VR experience. Before the global pandemic, 12 people travelled regularly as a passenger weekly,
and 10 people have a frequent trip length from 30 minutes to one hour.
In the car, the participants were introduced to our hygiene concept and study procedure, followed by a demographic
questionnaire. They were then instructed to put on the ECG respiratory band to record the
baseline data for 5 minutes. In a 5-min trial round while the car was parked, they were asked
to wear the headset and familiarise themselves with hitting targets in their central views.
After checking seat belts, the experimenter drove the participant towards the city highway.
Upon instruction, the participant put on the HMD again and continued the next condition.
They experienced three dwell-time durations with each pair appearing eight times in a randomised
order. When the participant ended a condition and took off the headset, the experimenter exited the
highway, parked the car, and record the ECG data in a stationary environment.
Meanwhile, the participants filled out the questionnaires.
The procedure was repeated for the remaining range conditions. After this, the experimenter conducted
a semi-structured interview. The entire study took about 100 minutes. While performing the
HMD tasks, participants accelerated their head movements as the range widened. In comparison,
they completed the task with a minimum deviation of 0.06 s and 0.04m/s in condition B. Participants
performed best in condition B, with the least deviation in the calculated time and speed.
However, their voluntary movements imply a demanded range from their central views
smaller than 25 degrees on the Y axis and 25 to 50 degrees on the X axis. A Repeated Measures
ANOVA test revealed significant differences in Heart Rate Variability. Post hoc testing
revealed that RMSSD decreased significantly after the participants put on the HMD.
High values of the Stress Index and low values of the RMSSD in Condition A signalises mental stress
and motion sickness. Participants reported more severe motion sickness with a higher total score
in a wider range of head movements. However, an ANOVA test found no significance. Overall,
our participants reported a moderately to highly comfortable and engaging experience with a low
level of motion sickness across head motion ranges and orientations. Participants found the Y-axis
overall less comfortable in condition C, where they also felt more motion sick in comparison
to condition A. ANOVA tests showed significant differences in these two reports. Besides, we
found overall moderate to high engagement across conditions. Participants also felt moderately
present in the virtual environment. In addition, we found descending trends in the ratings of the
pragmatic quality and the concentration, as the head movement range increased from condition A,
B, to C. ANOVA tests revealed significance in the pragmatic quality across ranges . In the
interview, participants reported cumulative feelings of discomfort after the ride,
such as ...I didn't feel any sickness during the VR experience, but I felt motion sick after taking
off the headset. Participants assessed the yaw movement more positively than the pitch axis.
Nine people found the yaw movement "...easy and more natural", while three described the pitch
movement uncomfortable and had to "...move the body to reach the target". Furthermore, five
people bumped into the car ceiling or the side door in condition C. This wider head movement made
them aware of the real world and decreased the feeling of presence. They reported that "...when
I crashed into the car roof I didn't feel engaged as well as "...looking up and down made me feel
the weight of the HMD" Participants preferred 0.3s and 1s. Our results from this head-gaze-based
task in a mobile field study align with prior VR studies suggesting 1s or less for simple tasks.
Condition B performed moderately well in both physiological and subjective measurements,
which we consider the best trade-off between motion sickness and engagement.
Thus, we propose to design the main interaction area within plus minus 50 degrees along the X-
and Y-axis; Based on the detected real-time performance of the passenger s head movements,
the UI could trigger a guidance mode. The user can follow the emerging visual motion cues in the
peripheral area synchronised with the real-time car movements. Therefore, we propose to design the
UIs beyond the activities and consider the visual cues to guide the passenger s head movements
for counteracting motion sickness; Faced with the upcoming concept of self-driving carsickness,
future research will probably address large and multiple displays buit into cars,
or brought-in HMDs. Our automotive virtual field study approach may be a future research direction
for investigating motion sickness in rear-seat HMD usage. In this field study, we used an accessible
VR HMD with specific technical parameters. A newer model with a wider field of view and
higher resolution might improve the user s visual perception and further influence our
results. Future work can replicate the study with newer headset models. Faced with the challenge
of balancing an effective elicitation of motion sickness while ensuring our participants safety,
we pre-screened for vulnerable passengers and thus limited and skewed our sample. We
call for invetigation on passengers with a high proness to motion sickness in future studies.
Out of safety concerns, we selected a city highway, with relatively controlled traffic
conditions in comparison to stop-and-go traffic on urban streets. Our results are, therefore,
limited to such a traffic environment. We call for future studies on dynamic traffic conditions.
Moreover, our current VR prototype achieved only a moderate level of presence across groups.
Future studies can explore the design of the head-gaze targets embedded into the virtual
environment to enhance the presence. Different from the implemented discrete level of head range,
we plan for a continuous head motion in a follow-up study
to lift restrictions on the freedom of head movement in reality.
Future studies can explore more sensitive physiological measurements of motion sickness
to improve the study validity by controlling the potential impact of physical activity.
To conclude, based on the recorded physiological and subjective data, we found a good trade-off for
rear-seat passenger head movement, characterised by the range of 50 with the speed of 1.95m/s,
a preferred motion around the yaw axis, and a dwell-time duration of 1s. Thank you very much.