Wisconsin Statutes Vehicles (Ch. 340 to 351) § 347.08. Determining the visibility distance and mounted height of lamps

(1) Whenever this chapter states a requirement as to distance from which certain lamps and devices shall render objects visible or within which such lamps or devices shall be visible, such distance shall be measured during hours of darkness under normal atmospheric conditions and upon a straight, level, unlighted highway unless a different time, direction or condition is expressly stated.

(2) Whenever this chapter requires a lamp or device to be mounted at a certain height, the distance shall be measured from the center of the lamp or device to the level ground upon which the vehicle stands when such vehicle is without load.