Tilt-rate perception in vehicle simulation: the role of motion, vision and attention

In vehicle simulation (flight, driving) simulator tilt is used to reproduce sustained acceleration. In order to feel realistic, this tilt is performed at a rate below the tilt-rate detection threshold, which is usually measured in darkness, and assumed constant. However, it is known that many factors affect the threshold, like visual information, simulator motion in additional directions, or active vehicle control. Since all these factors come together in vehicle simulation, we aimed at investigating the effect of each of these factors on roll-rate detection threshold during simulated curve driving. The experiment was conducted on a motion-based driving simulator. Roll-rate detection thresholds were determined under four conditions: (i) roll only in darkness; (ii) combined roll/sway in darkness; (iii) combined roll/sway and visual information whilst passively moved through a curve; (iv) combined roll/sway and visual information whilst actively driving around a curve. For all conditions, motion was repeatedly provided and ten participants reported the detection of roll in a yes-no task. Thresholds were measured by adjusting roll-rate saturation value according to a single-interval adjustment matrix (SIAM) at every trial. Mean detection threshold for roll-rate increased from 0.7 deg/s with roll only (i) to 6.3 deg/s in active driving (iv) (mean threshold was 3.9 deg/s and 3.3 deg/s in conditions (ii) and (iii) respectively). However, large differences between participants were observed: for some the threshold did not increase from passive to active driving; while for others about 3 times higher threshold was measured, and lower level of attention was reported on questionnaires. We conclude that tilt-rate perception in vehicle simulation is affected by the combination of different simulator motions. Similarly, an active control task seems to increase detection threshold for tilt-rate, i.e. impair motion sensitivity. Results suggest that this is related to the level of attention during the task