(a) Whenever this article declares the required distance from which certain lights and devices shall render objects visible or within which such lights or devices shall be visible, such provisions shall apply during the times stated in Code Section 40-8-20 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.

(b) Except as provided in subsection (c) of this Code section, whenever this article declares the required mounted height of lights or devices, it shall mean the distance from the center of such light or device to the level ground upon which the vehicle stands when such vehicle is without a load.

(c)(1) As used in this subsection, the term "wrecker" means any vehicle designed to tow other vehicles.

(2) Except as provided in paragraph (3) of this subsection, the taillights required by Code Section 40-8-23, the brake lights required by Code Section 40-8-26, and the rear turn signal devices required by Code Section 40-8-26 shall be permanently mounted on a wrecker so as to be visible above any vehicle being towed by such wrecker by the drivers of vehicles following such wrecker.

(3) If a wrecker is not permanently equipped with lights as required by paragraph (2) of this subsection, then whenever a wrecker is towing another vehicle temporary taillights, brake lights, and rear turn signals which function so as to signal the actions of the wrecker shall be attached to the vehicle being towed so as to be visible by the drivers of vehicles following such wrecker.