BICYCLE LIGHTS LAW REQUIRMENTS IN Iowa
In US the bike lights die required by Law if you reading in low light conditions, The light can be attached to either the bike or to the cyclist but must be visible at least 500 feet to the front of the bicyde, so be careful how you position the light. Additional lighting must be consistent with the law specifying required lights and reflectors, so a rear light must be red.
LIGHTS, SIRENS OR WHISTLES
A headlight and taillight or red reflector is required from sunset to sunrise or when conditions reduce visibility. Lights must be visible from 300′ away. Sirens or whistles are not permitted.
321.397 LAMPS ON BICYCLES.
Every bicycle shall be equipped with a lamp on the front exhibiting a white light, at the times specified in section 321.384, visible from a distance of at least three hundred feet to the front and with a lamp on the rear exhibiting a red light visible from a distance of three hundred feet to the rear; except that a red reflector may be used in lieu of a rear light. A peace officer riding a police bicycle is not required to use either front or rear lamps if duty so requires.
321.384 WHEN LIGHTED LAMPS REQUIRED.
1. Every motor vehicle upon a highway within the state, at any time from sunset to sunrise, and at such other times when conditions such as fog, snow, sleet, or rain provide insufficient lighting to render clearly discernible persons and vehicles on the highway at a distance of five hundred feet ahead, shall display lighted headlamps as provided in section 321.415, subject to exceptions with respect to parked vehicles as hereinafter stated.