(Im)possibilities of studying carsickness in a driving simulator

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.