BICYCLE LIGHTS LAW REQUIRMENTS IN Vermont
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.
2012 Vermont Statutes
Title 23 Motor Vehicles
Chapter 13 OPERATION OF VEHICLES
§ 1141 Equipment on bicycles
(a) A person shall not operate a bicycle at nighttime from one-half hour after sunset until one-half hour before sunrise unless the bicycle or the bicyclist is equipped with a lamp on the front which emits a white light visible from a distance of at least 500 feet to the front. In addition, bicyclists shall operate during these hours with either a lamp on the rear of the bicycle or bicyclist which emits a flashing or steady red light visible at least 300 feet to the rear, or with reflective, rear-facing material or reflectors, or both, with a surface area totaling at least 20 square inches on the bicycle or bicyclist and visible at least 300 feet to the rear.