Wisconsin Statutes Vehicles (Ch. 340 to 351) § 347.13. Tail lamps and registration plate lamps

(1) No person may operate a motor vehicle, mobile home, or trailer or semitrailer upon a highway during hours of darkness or during a period of limited visibility unless the motor vehicle, mobile home, or trailer or semitrailer is equipped with at least one tail lamp mounted on the rear which, when lighted during hours of darkness, emits a red light plainly visible from a distance of 500 feet to the rear. No tail lamp may have any type of decorative covering that restricts the amount of light emitted when the tail lamp is in use. No vehicle originally equipped at the time of manufacture and sale with 2 tail lamps may be operated upon a highway during hours of darkness or during a period of limited visibility unless both lamps are in good working order. This subsection does not apply to any type of decorative covering originally equipped on the vehicle at the time of manufacture and sale.

(2) Every tail lamp on a vehicle shall be located at a height of not more than 72 inches nor less than 20 inches.

(3) No person shall operate on a highway during hours of darkness any motor vehicle upon the rear of which a registration plate is required to be displayed unless such motor vehicle is equipped with a lamp so constructed and placed as to illuminate with a white light the rear registration plate and render it clearly legible from a distance of 50 feet to the rear. Such lamp may be incorporated as part of a tail lamp or may be a separate lamp.

(4) Tail lamps and registration plate lamps shall be so wired as to be lighted whenever the headlamps or auxiliary driving lamps are lighted. In a tractor-semitrailer combination, 2 switches may be employed, one to activate semitrailer lamps and one to activate tractor lamps.