BICYCLE LIGHTS LAW REQUIRMENTS IN Alaska
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.
"13 AAC 04.320. Headlights. c) A bicycle, when ridden at the times when lights are required under 13AAC 04.010(a) (1) & (2), must be equipped with at least one light on the front of the bicycle, emitting white light visible from a distance of at least 500 feet in front of the bicycle under normal atmosphere conditions.
13 AAC 04.325. Taillights. a) A bicycle must be equipped with a taillight which displays a red light visible 500 feet to the rear of a bicycle.
13 AAC 04.335. Reflectors. b) Every bicycle, when ridden at a time when lights are required under 13AAC 04.010, must be equipped with a red reflector on the rear of the bicycle and reflective material visible from the sides of the bicycle meeting the visibility requirements of 13AAC 04.010 (a) of this chapter. Nothing in this subsection prohibits the use of additional reflectors or reflective materials upon a bicycle."