D.C. Mun. Regs. tit. 18 § 709
Each reflector on any vehicle referred to in § 707 shall be of such size and characteristics and so maintained as to be readily visible at night-time from all distances within five hundred feet (500 ft.) to fifty feet (50 ft.) from the vehicle when directly in front of upper beams of head lamps. (NOTE: see § 715 )
Reflectors required to be mounted on the front and sides of the vehicle shall reflect the required color of light to the front and sides, and those mounted on the rear shall reflect a red color to the rear.
Front and rear clearance lamps shall be capable of being seen and distinguished under normal atmospheric conditions at the times lights are required at a distance of five hundred feet (500 ft.) from the front and rear of the vehicle, respectively
Side marker lamps shall be capable of being seen and distinguished under normal atmospheric conditions at the times lights are required at a distance of five hundred feet (500 ft.) from the side of the vehicle on which mounted.
D.C. Mun. Regs. Tit. 18, § 709