1.    Whenever requirement is hereinafter declared as to distance from which certain lamps and devices must render objects visible or within which such lamps or devices must be visible, said provisions apply during the times stated in section 39-21-01 in respect to a vehicle without load when upon a straight, level, unlighted highway under normal atmospheric conditions unless a different time or condition is expressly stated.

2.    Whenever requirement is hereinafter declared as to the mounted height of lamps or devices it means from the center of such lamp or device to the level ground upon which the vehicle stands when such vehicle is without a load.