D.C. Mun. Regs. tit. 18 § 716
Head lamps arranged to provide a single distribution of light not supplemented by auxiliary driving lamps shall be permitted on motor vehicles manufactured and sold prior to January 1, 1950, in place of multiple-beam road-lighting equipment specified in § 715, if the single distribution of light complies with the requirements and limitations set forth in this section.
The head lamps shall be so aimed that when the vehicle is not loaded none of the high-intensity portion of the light shall, at a distance of twenty-five feet (25 ft.) ahead, project higher than a level of five inches (5 in.) below the level of the center of the lamp from which it comes, and in no case higher than forty-two inches (42 in.) above the level on which the vehicle stands, at a distance of seventy-five feet (75 ft.) ahead.
The intensity shall be sufficient to reveal persons and vehicles at a distance of at least one hundred feet (100 ft.) ahead on a straight, level road.
D.C. Mun. Regs. Tit. 18, § 716