Idaho Code § 49-917
Every vehicle, including animal-drawn vehicles and other vehicles not specifically required by the provisions of this chapter to be equipped with lamps or other lighting devices, shall at all times specified in section 49-903, Idaho Code, be equipped with at least one (1) lamp displaying a white light visible from a distance of not less than five hundred (500) feet to the front of the vehicle, and shall also be equipped with two (2) lamps displaying a red light visible from the same distance to the rear of the vehicle, or as an alternative, one (1) lamp displaying a red light visible from the same distance to the rear and two (2) red reflectors visible for distances of one hundred (100) to six hundred (600) feet to the rear when illuminated by the upper beams of head lamps.
Idaho Code § 49-917