Iowa Code § 321.421: Special restrictions on lamps.

1. Any lighted lamp or illuminating device upon a motor vehicle other than headlamps, spot lamps, or auxiliary driving lamps which projects a beam of light of an intensity greater than three hundred candlepower shall be so directed that no part of the beam will strike the level of the roadway on which the vehicle stands at a distance of more than seventy-five feet from the vehicle.

2. A person convicted of a violation of this section is guilty of a simple misdemeanor punishable as a scheduled violation under section 805.8A, subsection 3.