D.C. Mun. Regs. r. 18-715
Except as provided otherwise in this section, the headlamps, the auxiliary driving lamp, the auxiliary passing lamp, or combination of such lamps on motor vehicles other than autocycles, motorcycles or motorized bicycles shall be so arranged that the driver may select at will between distributions of light projected to different elevations. These lamps may be so arranged that the selection can be made automatically, subject to the limitations stated in this section.
There shall be an uppermost distribution of light, or composite beam, so aimed and of such intensity as to reveal persons and vehicles at a distance of at least three hundred fifty feet (350 ft.) ahead for all conditions of loading.
There shall be a lowermost distribution of light, or composite beam, so aimed and of sufficient intensity to reveal persons and vehicles at a distance of least one hundred feet (100 ft.) ahead; and on a straight, level road under any condition of loading, none of the high-intensity portion of the beam shall be directed to strike the eyes of an approaching driver.
Each new motor vehicle, other than a autocycle, motorcycle or motor-driven cycle, which has multiple-beam road lighting equipment shall be equipped with a beam indicator, which shall be lighted whenever the uppermost distribution of light from the head lamps is in use, and shall not otherwise be lighted. This indicator shall be so designed and located that when lighted it will be readily visible without glare to the driver of the vehicle so equipped.
Each motor vehicle equipped with multiple-beam head lamps operating on the highways of the District when lights are required shall use the lower or city-driving beam.
D.C. Mun. Regs. r. 18-715