When the monitor camera or the driver are lit by sunlight or there are repeated changes in brightness either by sunlight or shadow.

When there is an obstruction between the driver’s face and the monitor camera.

When more than one face is recognised near the driver’s seat (for example, a passenger is leaning toward the driver).

When the driver’s face cannot be seen correctly by the monitor camera. It may occur when the face is blocked by the hand or when the driver is in a posture where position of the face is difficult to recognise by the camera.