D.C. Mun. Regs. r. 18-705
Each motor vehicle, trailer, semi-trailer, and pole trailer, and any other vehicle which is being drawn at the end of a train of vehicles, shall be equipped with at least one (1) tail lamp mounted on the rear, which, when lighted as required, shall emit a red light plainly visible from a distance of five hundred feet (500 ft.) to the rear; Provided, that in the case of a train of vehicles, only the tail lamp on the rear most vehicle need actually be seen from the distance specified.
Each vehicle of the types listed in § 705.1 registered in the District of Columbia and manufactured or assembled after September 15, 1955; other than truck tractors manufactured or assembled prior to January 1, 1968, autocycles, motorcycles, and motor-driven cycles; shall be equipped with at least two (2) tail lamps mounted on the rear, on the same level, and as widely spaced as practicable, which, when lighted as required, shall comply with the provisions of this section.
Each tail lamp on each vehicle shall be located at a height of not more than seventy-two inches (72 in.) or less than fifteen inches (15 in.), measured from the center of the lamp to the level ground upon which the vehicle stands when the vehicle is without a load.
Either a tail lamp or a separate lamp shall be so constructed and placed as to illuminate with a white light the rear registration plate and render it clearly legible from a distance of fifty feet (50 ft.) to the rear.
Any tail lamp or tail lamps, together with any separate lamp for illuminating the rear registration, shall be wired to be lighted whenever the head lamps or auxiliary driving lamps are lighted.
D.C. Mun. Regs. r. 18-705