Background Carsickness is a potential barrier to the acceptance of automated driving as it turns drivers into passengers, thus making them more susceptible to motion sickness. However, most of our current knowledge of how vehicle motion causes motion sickness comes from seasickness studies, using vertical motion only. Some more recent studies have investigated the relationship between horizontal accelerations and motion sickness, but with inconsistent methodology and sometimes conflicting results. Objective To quantify the effects of acceleration frequency and magnitude for periodic accelerations along the longitudinal, lateral, and vertical axes in a large sample of participants, using consistent methodology throughout. Methods In three separate experiments, in total 107 participants were exposed to sinusoidal accelerations along either the longitudinal, lateral or vertical axis with different combinations of motion frequency and peak acceleration. Motion frequency was varied between 0.03 and 3.2 Hz, with peak acceleration ranging from 0.5 to 4.0 m/s 2 . Motion sickness was measured during motion exposure using the Motion Illness Symptoms Classification (MISC) scale, while the Simulator Sickness Questionnaire (SSQ) and a visual analogue Discomfort scale were administered after each motion exposure. Results Motion sickness severity due to motion exposure was similar for the three motion axes. All three outcome measures showed a clear motion frequency dependency, with motion sickness in general most severe for frequencies around 0.2 Hz. However, significant motion sickness symptoms were observed for the entire frequency range tested. The frequency dependency was less clear for lateral motion than for longitudinal and vertical motion. Higher accelerations led to more severe motion sickness, with the rate of increase decreasing when accelerations became higher. Conclusions Our results show that motion sickness due to periodic linear accelerations occurs along all three cardinal axes and that it depends on motion frequency. This frequency dependency was less clear for lateral motion than for longitudinal and vertical motion. Our results have important implications for both predictive models of motion sickness as well as for applications in automated vehicles.

To perceive orientation relative to gravity, we combine sensory information with weights proportional to each cue's reliability. However, reliability alone does not fully determine a cue's weight. When asking observers to orient a visual rod parallel to the orientation of gravity in the presence of a static (tilted frame) or dynamic (rotating disc) distractor, some make much larger deviations into the direction of the distractor than others. This idiosyncratic weighting of cues for the perception of verticality has been explained by an individual trait: visual field dependence. However, it can be questioned whether the static and dynamic distractor effects are based on the same mechanism. If they are, changing the depth position of the distractor should induce a similar change in the weighting of static and dynamic visual cues for judging verticality. To test this, we placed the distractors at a different depth than the rod and reversed their depth order while keeping their retinal extent constant. This change influenced the two distractor effects differently: the effect of the disc was considerably larger when it was in the background, whereas the effect of the frame reduced. Furthermore, the effect of depth order did not show a significant correlation between the two distractors. Our findings thus suggest that static and dynamic distractor effects are based on at least partly different mechanisms, implying that there is not a single visual dependence.

Motion sickness may prevent the adoption of automated vehicles, as passengers are more susceptible than drivers. Predicting individual susceptibility from vehicle motion is challenging due high variability between people. There is a need to measure passengers’ motion sickness, preferably objectively and unobtrusively. Biomarkers, the physiological responses to motion sickness, could provide a solution. We developed and evaluated a camera-based system using electro-optical and infrared imaging to measure facial skin temperature unobtrusively. The relationship between facial skin temperature in different regions of the face and motion sickness was determined by exposing participants (n = 14) to off-vertical axis rotation, which elicited severe nausea symptoms for most participants. While temporal patterns differed between participants, subjective ratings of motion sickness were specifically and consistently inverse-related to forehead skin temperature. The potential and challenges of using infrared cameras to objectively and unobtrusively assess motion sickness during autonomous driving are discussed.

This study evaluated the suitability of the vibration dose value (VDV) and action and limit values from the EU Directive 2002/44/EC in assessing lower back health risks due to repeated shocks using common horse riding as an example. The difference between pelvis- and saddle-based VDV calculations was assessed. VDVs were calculated from accelerations measured using inertial measurement units (IMUs) on the saddle and the rider’s pelvis during walking (30 min) and cantering (10 min). Saddle and pelvis VDVs were similar, 12–31 m/s1.75 for walking and 46–69 m/s1.75 for cantering. Accelerations reached the action value (9.1 m/s1.75) within 03:16 min of walking and 00:08 min of cantering. Accelerations reached the limit value (21 m/s1.75) within 30:00 min or 00:26 min of cantering. Although VDV reached limits quickly, walking and cantering are generally harmless for the lower back. Application of the VDV and associated limits for repeated shocks assessment might need reconsideration.

This study examines self-motion perception incorporated into motion sickness models. Research on modeling self-motion perception and motion sickness has advanced independently, though both are thought to share neural mechanisms, making the construction of a unified model opportune. Models based on the Subjective Vertical Conflict (SVC) theory, a refinement of the neural mismatch theory, have primarily focused on motion sickness, with limited validation for self-motion perception. Emerging studies have begun evaluating the perceptual validity of these models, suggesting that some models can reproduce perception in specific paradigms, while they often struggle to jointly capture motion perception and sickness. One prior study demonstrated that one of the SVC models could replicate illusory tilt during centrifugation, while others produced unrealistic responses, such as persistent tilt after motion cessation. In reality, under steady-state conditions such as being motionless, perceived motion is expected to settle to an appropriate state regardless of prior states. Based on the idea that this behavior is closely related to the equilibrium points and stability of the model dynamics, this study theoretically analyzed 6DoF-SVC models with a focus on them. Results confirmed that only one model ensures convergence from any state to a unique equilibrium point corresponding to plausible perception. In contrast, other SVC models and a conventional self-motion perception model converged to values dependent on earlier states. Further analysis showed that only this model captured both the somatogravic and Ferris wheel illusion. In conclusion, this 6DoF-SVC model unifies motion perception and sickness modeling, with theoretical convergence of the perceptual state.

Car passengers suffer much more from motion sickness compared to car drivers, presumably because drivers can better anticipate the car’s motions. Visual and auditory cues that announce upcoming motions have been demonstrated to mitigate motion sickness. In automated vehicles, vibrotactile cues might be more desirable. However, prior studies provided mixed evidence regarding their effectiveness. In this study, we directly compared the effectiveness of anticipatory auditory and vibrotactile cues. We determined their effectiveness by examining self-reported motion sickness from anticipatory sessions with auditory or vibrotactile cues announcing the onset and direction of upcoming motion relative to a control session. Our preregistered analysis did not show a significant difference in mitigation between the cues but also no significant overall effect. As this lack of an effect may be due to limited statistical power, we performed an internal meta-analysis. This analysis demonstrated a small overall effect of anticipatory cues. We conclude that it is worthwhile to investigate how their effectiveness can be enhanced.

Personnel shortages in the military sector require deploying soldiers as effectively as possible. Increased vehicle automation, e.g. for displacements or for resupply convoys, can improve this effectiveness by lowering the mental load needed for driving. Drivers of automated vehicles resemble passengers and are thereby more susceptible to motion sickness than drivers of non-autonomous vehicles. It is useful to monitor potential motion sickness, to ensure personnel arrive fit for duty at their destination. Therefore, a system to automatically detect the presence of motion sickness would be beneficial. In this paper, we introduce a camera-based system that uses electro-optical (EO) and infrared (IR) video sets to monitor facial skin temperature and respiratory rate as a step towards camera-based motion sickness monitoring in autonomous vehicles. Our proof-of-concept system obtained sufficient measurement accuracy for use in an experimental setting in which participants were subjected to a condition that induced motion sickness. We discuss the successes and challenges encountered during system set-up and data analysis, and share insights relevant to the envisioned application in an autonomous vehicle. Specifically, we compare recordings with and without subject motion caused by the motion sickness inducing condition and discuss measurement inaccuracies that might be encountered because of IR thermal drift. Additionally, we reflect on obstacles that can arise when employing an EO/IR monitoring system in a military context.

Car passengers experience much more car sickness than car drivers. We assume that this is because drivers can better anticipate the car’s motions. Does helping passengers to anticipate the car’s motions then mitigate car sickness? Indeed, laboratory studies have shown that anticipatory cues which announce one-dimensional motions of a linear sled mitigate sickness to a small extent. Does this mitigation generalize to real car driving? We tested this in a car ride on a test track along a trajectory involving lane changes, accelerations, and decelerations. We show that vibrotactile cues mitigated car sickness in passengers. Auditory cues were less effective. The mitigating effect of the vibrotactile cue was considerable: a 40% decrease in car sickness symptoms, a larger effect than we found in the laboratory. Automated vehicles can predict their own motion very well. They could thus provide vibrotactile cues to mitigate car sickness in their passengers.

IntroductionTo date, no systematic review or meta-analysis has critically evaluated the relevance of using optokinetic after-nystagmus (OKAN) in diagnosis of vestibular disorders. To assess the role of OKAN in diagnosis of vestibular disorders, the OKAN time constant (TC) between patients with vestibular disorders and healthy participants will be compared.MethodsAutomated search strategies were carried out in the Embase, Medline PubMed, Web of Science, and Scopus databases from inception to December 2023. The following inclusion criteria were applied: (1) evaluation of OKAN in individuals with vestibular disorders, (2) clinical trials, and (3) inclusion of healthy individuals as the control group. Exclusion criteria were: (1) animal studies, (2) non-clinical trial study designs, (3) assessment of non-vestibular disorders, (4) no examination of OKAN TC, (5) only examination of healthy participants, (6) studies published in a language other than English, (7) no healthy participants as control group, (8) case reports, and (9) only abstract available. The random-effects model was used to pool the data. The Joanna Briggs Institute (JBI) Critical Appraisal Tools was used to assess the risk of bias. The quality assessment was performed with the aid of the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies, provided by NHLBI. The PRISMA guidelines were used as reporting guidelines. The main outcome of this study was the between-group mean difference (MDbetween) in OKAN TC and its 95% confidence interval between patients with vestibular disorders and healthy participants.ResultsSeven out of 244 screened articles were included that studied 289 participants. The overall mean difference (MD = −7.08) with a 95% CI of [−10.18; −3.97] was significant (p = 0.014). The heterogeneity was significant (p = 0.02). Quality assessment was generally good (76%). The risk of bias was low in five studies and moderate in two studies.ConclusionThe results demonstrate that OKAN TC is significantly shorter in patients with vestibular disorders compared to healthy controls. This finding is important for future research, particularly with the emergence of novel clinical tools and diagnostic syndromes.Systematic Reviewhttps://www.crd.york.ac.uk/prospero/display_record.php?RecordID=442695.

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The introduction of (fully) automated vehicles has generated a re-interest in motion sickness, given that passengers suffer much more from motion sickness compared to car drivers. A suggested solution is to improve the anticipation of passive self-motion via cues that alert passengers of changes in the upcoming motion trajectory. We already know that auditory or visual cues can mitigate motion sickness. In this study, we used anticipatory vibrotactile cues that do not interfere with the (audio)visual tasks passengers may want to perform. We wanted to investigate (1) whether anticipatory vibrotactile cues mitigate motion sickness, and (2) whether the timing of the cue is of influence. We therefore exposed participants to four sessions on a linear sled with displacements unpredictable in motion onset. In three sessions, an anticipatory cue was presented 0.33, 1, or 3 s prior to the onset of forward motion. Using a new pre-registered measure, we quantified the reduction in motion sickness across multiple sickness scores in these sessions relative to a control session. Under the chosen experimental conditions, our results did not show a significant mitigation of motion sickness by the anticipatory vibrotactile cues, irrespective of their timing. Participants yet indicated that the cues were helpful. Considering that motion sickness is influenced by the unpredictability of displacements, vibrotactile cues may mitigate sickness when motions have more (unpredictable) variability than those studied here.

(1) Background: It is difficult for accident investigators to objectively determine whether spatial disorientation may have contributed to a fatal airplane accident. In this paper, we evaluate three methods to reconstruct the possible occurrence of the somatogravic illusion based on flight data recordings from an airplane accident. (2) Methods: The outputs of two vestibular models were compared with the “standard” method, which uses the unprocessed gravito-inertial acceleration (GIA). (3) Results: All three methods predicted that the changing orientation of the GIA would lead to a somatogravic illusion when no visual references were available. However, the methods were not able to explain the first pitch-down control input by the pilot flying, which may have been triggered by the inadvertent activation of the go-around mode and a corresponding pitch-up moment. Both vestibular models predicted a few seconds delay in the illusory tilt from GIA due to central processing and sensory integration. (4) Conclusions: While it is difficult to determine which method best predicted the somatogravic illusion perceived during the accident without data on the pilot’s pitch perception, both vestibular models go beyond the GIA analysis in taking into account validated vestibular dynamics, and they also account for other vestibular illusions. In that respect, accident investigators would benefit from a unified and validated vestibular model to better explain pilot actions in accidents related to spatial disorientation.

Motion sickness in automated vehicles (AVs) represents a key Human Factors concern that will negatively impact the passenger experience and, ultimately, public acceptance. Minimizing or avoiding motion sickness altogether, therefore, becomes a strategic design goal. In this article we propose principal research questions that need to be addressed as part of a concerted effort to understand the causative factors of motion sickness and the need to develop and apply common protocols to accelerate knowledge and subsequent innovation in this field. With the ultimate goal to provide guidelines to inform the design of future vehicles, the International Organization for Standardization standard (ISO) 2631-1 (1997) is taken as the starting point. The current standard provides estimates of the likelihood of motion sickness as a function of vertical motion input only. However, in the context of AVs, and in particular in the light of anticipated non-driving-related activities in such vehicles, the current standard is of limited use: The model has not been validated for horizontal and rotational motions or any potential multi-axes interactions; The standard was derived on the basis of the percentage of passengers reaching the point of emesis while less severe levels of motion sickness are of greater interest and may show a different relationship between the frequency and acceleration; Modulating factors that are able to regulate, adjust, or adapt sickness levels are not included, in particular vision and the associated concept of anticipation, passenger orientation, and reclination angles. Finally, the accumulation of motion sickness knowledge in this field is severely hampered by the absence of consistent study protocols. We here propose the identification and development of appropriate vibration measurements and motion sickness assessment and evaluation methods.

BACKGROUND: The vestibular Coriolis illusion is a disorienting sensation that results from a transient head rotation about one axis during sustained body rotation about another axis. Although often used in spatial disorientation training for pilots and laboratory studies on motion sickness, little is known about the minimum required rotation rate to produce the illusion. OBJECTIVE: This study determined the perception threshold associated with the Coriolis illusion. METHODS: Nineteen participants performed a standardized pitching head movement during continuous whole-body yaw rotation at rates varying between 5 to 50 deg/s. The participants reported their motion sensation in relation to three hypothesized perception thresholds: 1) a sense of undefined self-motion, 2) a sense of rotation, and 3) a sense of rotation and its direction (i.e., the factual Coriolis illusion). The corresponding thresholds were estimated from curves fitted by a generalized linear model. RESULTS: On average threshold 1 was significantly lower (8 deg/s) than thresholds 2 and 3. The latter thresholds did not differ from each other and their pooled value was 10 deg/s. CONCLUSIONS: The Coriolis illusion is perceived at yaw rates exceeding 10 deg/s using a pitching head movement with 40 deg amplitude and 55 deg/s peak velocity. Model analysis shows that this corresponds to an internal rotation vector of 6 deg/s. With this vector the Coriolis perception threshold can be predicted for any other head movement.

Motion sickness is known under several names in different domains, such as seasickness, carsickness, cybersickness, and simulator sickness. As we will argue, these can all be considered manifestations of one common underlying mechanism. In recent years, it has received renewed interest, largely due to the advent of automated vehicles and developments in virtual reality, in particular using head-mounted displays. Currently, the most widely accepted standard to predict motion sickness is ISO 2631-1 (1997), which is based on studies on seasickness and has limited applicability to these newer domains. Therefore, this paper argues for extending the ISO standard to cover all forms of motion sickness, to incorporate factors affecting motion sickness, and to consider various degrees of severity of motion sickness rather than just emesis. This requires a dedicated standard, separate from other effects of whole-body vibration as described in the current ISO 2631-1. To that end, we first provide a sketch of the historical origins of the ISO 2631-1 standard regarding motion sickness and discuss the evidence for a common mechanism underlying various forms of motion sickness. After discussing some methodological issues concerning the measurement of motion sickness, we outline the main knowledge gaps that require further research.

Various studies have demonstrated a role for cognition on self-motion perception. Those studies all concerned modulations of the perception of a physical or visual motion stimulus. In our study, however, we investigated whether cognitive cues could elicit a percept of oscillatory self-motion in the absence of sensory motion. If so, we could use this percept to investigate if the resulting mismatch between estimated self-motion and a lack of corresponding sensory signals is motion sickening. To that end, we seated blindfolded participants on a swing that remained motionless during two conditions, apart from a deliberate perturbation at the start of each condition. The conditions only differed regarding instructions, a secondary task and a demonstration, which suggested either a quick halt ("Distraction") or continuing oscillations of the swing ("Focus"). Participants reported that the swing oscillated with larger peak-to-peak displacements and for a longer period of time in the Focus condition. That increase was not reflected in the reported motion sickness scores, which did not differ between the two conditions. As the reported motion was rather small, the lack of an effect on the motion sickness response can be explained by assuming a subthreshold neural conflict. Our results support the existence of internal models relevant to sensorimotor processing and the potential of cognitive (behavioral) therapies to alleviate undesirable perceptual issues to some extent. We conclude that oscillatory self-motion can be perceived in the absence of related sensory stimulation, which advocates for the acknowledgement of cognitive cues in studies on self-motion perception.

Motion sickness has gained renewed interested in the context of the developments in vehicle automation in which we are witnessing a transition from a driver-centric to passenger-centric design philosophy. As a corollary, motion sickness can be expected to become considerably more prevalent which creates a hurdle towards the successful introduction of vehicle automation and its ultimate socio-economic and environmental benefits. We here review early proof-of-concept studies into the beneficial effects of providing passenger with predictive motion cues as an elegant and effective method to reduce motion sickness in future vehicles. Future design parameters are discussed to finetune such cues not only for optimum effectiveness but, importantly, also for acceptance including sensory modality, timing, information detailing, and personalization.

Motion sickness has a dominant contribution to the broader concept of discomfort when self-motion is at issue, for example when travelling in a self-driving car. Recent studies are devoted to finding ways to mitigate motion sickness even though the relationship between the different types of scales used to measure motion sickness is largely overlooked. For this reason, we here compared two major types of self-report rating scales: those measuring general unpleasantness and those measuring specific symptomatology. For up to 30 minutes of ongoing motion stimulation, we found that 1) symptoms generally manifested in a fixed order, while unpleasantness seemed to increase non-monotonically, and 2) symptoms that manifested later were generally reported as more unpleasant, except for nausea onset. The onset of nausea was systematically rated less unpleasant than the preceding pre-nausea symptoms. This indicates that unpleasantness does not monotonically increase during the progression of motion sickness symptoms. Studies having used the two different types of scales can accordingly not directly be compared, particularly at nausea onset. Our results imply that rating how bad someone feels is not the equivalent of rating how close someone is to the point of vomiting.

When studying (the effectiveness of countermeasures to) carsickness in a simulator, it currently remains a question whether results still hold true in a real car. This question not only concerns its practical consequences, but the scientific interest in the underlaying mechanisms as well. By reckoning previous observations and new insights focussing on the differences between simulator and car motion as well their Out-the-Window (OtW) visuals, this paper nuances the assumption that (moving base) simulators can be useful in research on driving comfort in autonomous vehicles. It elaborates on six specific issues: 1) the use of fixed base simulators, 2) motion cueing, 3) linear displacement limitations, 4) display limitations, 5) perceptual scaling of visual and vestibular cues, and 6) physical and visually induced self-tilt. The overall conclusion is that only without OtW artificial visuals and when true car motion can be replicated, it is possible to elicit carsickness in a simulator. If motion is limited by displacement, sickness is most severe at 0.35 Hz. Whenever motion cueing and/or artificial OtW visuals are applied, sickness elicited is better described as simulator sickness, then defined as sickness only occurring during the simulated, but not during the real ride.

About two in three people have experienced carsickness at some point in their life (Reason \u0026 Brand, 1975). Little is known about current numbers of sufferers, cultural differences, or which modulating factors are being perceived as most relevant. Therefore, given a global increase of interest in carsickness driven by the development of automated vehicles, this survey intended to assess the status quo of carsickness in different parts of the world. We conducted an online survey with N = 4,479 participants in Brazil, China, Germany, UK and USA. 46% of participants indicated they had experienced some degree of carsickness in the past five years as a passenger in a car. When including childhood experiences, this rate increased to 59%, comparable to the 1975 findings by Reason and Brand. The highest and lowest incidence of carsickness was reported in China and Germany, respectively. In all countries, men and older participants reported a lower incidence of carsickness as compared to females and younger participants. The main modulating factors were found to be driving dynamics, visual activities, and low air quality. This study showed that carsickness still affects about 2/3 of passengers and discusses how its occurrence relates to in-transit activities and other modes of transport. The research provides a sound basis to further study how carsickness develops and to investigate countermeasures to potentially reduce it.