Is it Illegal to Ride a Bike At Night Without a Light?

Wisconsin bike light law requires a white front light visible from 500 feet and a red rear reflector. In Lieu of a reflector or in addition a person riding a bike in Wisconsin can use a red rear light that is either solid or flashing and visible from 500 feet. A great Madison, WI company named Planet Bike makes some really nice and very bright lights.

347.489  Lamps and other equipment on bicycles and other vehicles and devices.

(1)  No person may operate a bicycle, motor bicycle, personal delivery device, electric scooter, or electric personal assistive mobility device upon a highway, sidewalk, bicycle lane, or bicycle way during hours of darkness unless the bicycle, motor bicycle, personal delivery device, electric scooter, or electric personal assistive mobility device is equipped with or, with respect to a bicycle or motor bicycle, the operator is wearing, a lamp emitting a white light visible from a distance of at least 500 feet to the front of the bicycle, motor bicycle, personal delivery device, electric scooter, or electric personal assistive mobility device. A bicycle, motor bicycle, personal delivery device, electric scooter, or electric personal assistive mobility device shall also be equipped with a red reflector that has a diameter of at least 2 inches of surface area or, with respect to an electric scooter or an electric personal assistive mobility device, that is a strip of reflective tape that has at least 2 square inches of surface area, on the rear so mounted and maintained as to be visible from all distances from 50 to 500 feet to the rear when directly in front of lawful upper beams of headlamps on a motor vehicle. A lamp emitting a steady or flashing red light visible from a distance of 500 feet to the rear may be used in lieu of the red reflector.