MO Rev Stat § 307.128 (2021)
2021 Missouri Revised Statutes|Title XIX - Motor Vehicles, Watercraft and Aviation|Chapter 307 - Vehicle Equipment Regulations|Section 307.128 - Motorcycle headlamp modulation permitted, when — labeling requirements — auxiliary lighting.

Effective - 28 Aug 2015, 2 histories   307.128. Motorcycle headlamp modulation permitted, when — labeling requirements — auxiliary lighting. — 1. A headlamp on a motorcycle may be wired to modulate either the upper beam or the lower beam from its maximum intensity to a lesser intensity provided that:  (1) The rate of modulation shall be two hundred forty plus or minus forty cycles per minute;  (2) The headlamp shall be operated at a maximum power for fifty to seventy percent of each cycle;  (3) The lowest intensity at any test point shall not be less than seventeen percent of the maximum intensity measured at the same point;  (4) The modulator switch shall be wired in the power lead of the beam filament being modulated and not in the ground side of the circuit;  (5) Means shall be provided so that both the lower beam and the upper beam remain operable in the event of a modulation failure;  (6) The system shall include a sensor mounted with the axis of its sensing element perpendicular to a horizontal plane. Headlamp modulation shall cease whenever the level of light emitted by a tungsten filament operating at three thousand degrees kelvin is either less than two hundred seventy lux of direct light for upward pointing sensors or less than sixty lux of reflected light for downward pointing sensors. The light is measured by a silicon cell type light meter that is located at the sensor and pointing in the same direction as the sensor. A photo gray card is placed at ground level to simulate the road surface in testing downward pointing sensors;  (7) Means shall be provided so that both the lower and upper beam function at design voltage when the headlamp control switch is in either the lower or upper beam position when the modulator is off.  2. Each motorcycle headlamp modulator not intended as original equipment, or its container, shall be labeled with the maximum wattage, and the minimum wattage appropriate for its use. Additionally, each such modulator shall comply with the provisions of subdivisions (1) to (7) of subsection 1 of this section when connected to a headlamp of the maximum-rated power and headlamp of the minimum-rated power, and shall provide means so that the modulated beam functions at design voltage when the modulator is off. Instructions, with a diagram, shall be provided for mounting the light sensor including location on the motorcycle, distance above the road surface, and orientation with respect to the light.  3. Notwithstanding any other provision of law, subject to the requirements of subsection 4 of this section, a motorcycle may be equipped with, and an operator of a motorcycle may use, the following auxiliary lighting:  (1) Amber and white illumination;  (2) Standard bulb running lights; or  (3) Light-emitting diode pods and strips.  4. Lighting under subsection 3 of this section shall be:  (1) Nonblinking;  (2) Nonflashing;  (3) Nonoscillating; and  (4) Directed toward the engine and the drive train of the motorcycle to prevent interference with the driver's operation of the vehicle. ­­-------- (L. 2009 H.B. 253, A.L. 2015 H.B. 650)