Effects of Placing a CMS Monitor to Present Side and Rear View at the Driver-centered Position on Drivers’ Rearward Visual Behavior, Cognitive Load, and Mental Stress

The presentation range and position that could not be obtained using conventional side and rear mirrors can be obtained using the camera monitor system (CMS). Studies have proposed the effectiveness of a side–rear wide-view monitor that covers a wide angle from left to right. However, placing such a monitor in the same position as a conventional rear mirror creates an incongruent spatial relation problem because the driver seated on the right seat is forced to shift their gaze point to the left to perceive the right side. Thus, this study clarifies the effects of placing a side-rear wide-view monitor at the driver-centered (front of the driver) position on the drivers’ cognitive load, mental stress, and rearward visual behavior. Based on a driving simulator, the proposed side–rear wide-view monitor was set at three positions: the same position as a conventional rear mirror (vehicle-centered), in front of the driver (driver-centered), and in front of the driver and raised upward (driver-centered-up). Under the driver-centered condition, the oxygenated hemoglobin in the prefrontal cortex and the heart rate decreased and the eye movement became more frequent compared with the other conditions. By placing the side–rear wide-view monitor at the driver-centered position, the driver’s cognitive load and mental stress decreased and the rearward visual behavior was closer to that of skilled drivers. Placing the side–rear wide-view monitor at the driver-centered position shows some benefits for support of rearward recognition in perspective of the effects on cognitive load.