No person shall, during the period from one-half hour before sunrise to one-half hour after sunset, operate upon any highway any vehicle except fire apparatus, the load of which extends more than four feet beyond the rear of the body of such vehicle unless there is attached to the rear end of such load a red flag or cloth not less than twelve inches square so hung that the entire area is visible to the driver of a vehicle approaching from the rear, or, during the period of one-half hour after sunset to one-half hour before sunrise, and at any other time when, due to insufficient light or unfavorable atmospheric conditions, persons and vehicles on the highway are not clearly discernible at a distance of five hundred feet ahead, operate upon any highway any vehicle carrying a load which extends beyond the stationary floor of the body of such vehicle, unless a red light is attached to the rear end of such load, which light shall be plainly visible to the sides and rear for a distance of not less than five hundred feet. No motor vehicle with a commercial registration shall be permitted to remain stationary or be operated upon any highway when an animal not confined is carried or projects laterally outside of the body of such vehicle, or when any load or load-supporting device projects laterally beyond the edge of the body thereof. Violation of any provision of this section shall be an infraction.