This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
The rule
Alaska requires white lamp on the front, visible from a distance of at least 500 feet. For the rear, red reflector on the rear visible from a distance of 50 to 300 feet when illuminated by the lawful upper beams of a motor vehicle. a red rear lamp visible from 500 feet may be used in addition to the reflector. The rule applies whenever it is dark. See 13 AAC 02.455(c) (Bicycle lighting equipment).
The cheapest way to stay legal in Alaska is a USB-rechargeable front white light and a rear red light or reflector that meets the spec above. A $30 light set covers it.