Since all motion bases of simulator involve intrinsic physical limits, the lack of coupling between visual and inertial cues may be responsible for visuo-vestibular conflict, lowering presence in the virtual environment and increasing simulator sickness. In order to proportion the movements of the motion base and of the visual scenery, the present study aimed at characterizing the coupling between visual and inertial cues that generates a believable and realistic illusion of roll movement in a motorcycle simulator. In the experiment, participants (n=29) actively tuned the visual and physical tilt to achieve the best sensation of leaning, while the theoretical tilt of a real motorcycle (in a similar situation), the road curvature as well as the horizontal field of view (i.e., 60deg vs. 180deg) were manipulated. The results revealed different patterns of use of the visual scenery among riders (e.g., in tilting the visual horizon in the same or in the opposite direction of the displayed curve, or in keeping the visual horizon straight). The results are discussed in terms of the differential roles of tilting the visual and physical dimensions in creating a reliable illusion of riding among motorcyclists.
