Wisconsin Statutes Vehicles (Ch. 340 to 351) § 347.14. Stop lamps

(1) No person shall operate a motor vehicle, lightweight utility vehicle as defined in s. 346.94(21)(a)2., mobile home, or trailer or semitrailer upon a highway unless such motor vehicle, lightweight utility vehicle, mobile home, or trailer or semitrailer is equipped with at least one stop lamp mounted on the rear and meeting the specifications set forth in this section. The stop lamp on a mobile home or trailer or semitrailer shall be controlled and operated from the driver's seat of the propelling vehicle. A stop lamp may be incorporated with a tail lamp. No vehicle originally equipped at the time of manufacture and sale with 2 stop lamps shall be operated upon a highway unless both such lamps are in good working order.

(2) A stop lamp shall be so constructed as to be actuated upon application of the service or foot brake or separate trailer brake and shall emit a red or amber light plainly visible and understandable from all distances up to 300 feet to the rear during normal sunlight when viewed from the driver's seat of the vehicle following.