346.88 Obstruction of operator's view or driving mechanism.

(1) No person shall drive a vehicle when it is so loaded or when there are in the front seat such number of persons, or any persons so situated, as to obstruct the view of the operator to the front or to the sides or as to interfere with the operator having free use of both hands and feet to the operating mechanisms or controls of the vehicle.

(2) No passenger in a vehicle shall ride in such a position as to interfere with the operator's view ahead or to the sides or to interfere with the operator's control of the operating mechanism of the vehicle.

(3)

(a) No person shall drive any motor vehicle with any sign, poster or other nontransparent material upon the front windshield, front side wings, side windows in the driver's compartment or rear window of such vehicle other than a certificate or other sticker issued by order of a governmental agency. Such permitted sticker shall not cover more than 15 square inches of glass surface and shall be placed in the lower left-hand corner of the windshield; the left corner being on the driver's left when seated behind the wheel.

(b) No person shall drive any motor vehicle upon a highway with any object so placed or suspended in or upon the vehicle so as to obstruct the driver's clear view through the front windshield.

(c) No person shall drive any motor vehicle upon a highway so loaded or with any object so placed or suspended in or upon the vehicle so as to obstruct the driver's clear vision through the rear window unless such vehicle is equipped with an outside rear view mirror meeting the requirements of s. 347.40.

(d) Signal lamps used by authorized emergency vehicles shall not be considered a violation of this section.

(4) The windshield, side wings and side and rear windows of a motor vehicle shall be kept reasonably clean at all times.

Sub. (3) (a) creates an absolute prohibition on “any sign, poster or other nontransparent material upon the front windshield . . ." By contrast, sub. (4) states: “The windshield, side wings and side and rear windows of a motor vehicle shall be kept reasonably clean at all times." There is “no reason why the legislature would choose to ban oil change stickers, often no more than one or two square inches in size and placed in a top corner of a windshield, but require that same area of a windshield be only `reasonably' clean." Instead, sub. (3) (a) is interpreted to prohibit the attachment of signs, posters, and other items of a similar nature to the front windshield of a motor vehicle. State v. Houghton, 2015 WI 79, 364 Wis. 2d 234, 868 N.W.2d 143, 13-1581.

Sub. (3) (b), which requires that an object obstruct a driver's clear view to be a violation, does not mean that every object in a driver's clear view is a violation. Rather, sub. (3) (b) requires a material obstruction, even if minor, in order to be considered a violation of the statute. State v. Houghton, 2015 WI 79, 364 Wis. 2d 234, 868 N.W.2d 143, 13-1581.