Why is the interior light turned off while driving?

[LeGriffin]

Driving with the interior light off is due to obstructed vision and physiological reasons. Obstructed vision: The fundamental reason for turning off the light at night is that when the outside light is dim and the interior light is on, a physical imaging phenomenon occurs. The darkness outside acts like the back of a mirror, while the bright interior light acts like the front of the mirror, turning the windshield into a full-fledged mirror. Driving under these conditions can easily lead to traffic accidents. Physiological reasons: The human pupil controls the amount of light entering the eye. In bright light, the pupil constricts to prevent too much light from entering. In dim light, the pupil dilates to allow more light in for better vision. During nighttime driving, the dark interior allows the pupil to dilate, improving road visibility. If the interior light is turned on, the light causes the pupil to constrict, thereby worsening visibility.