Dash cams: no windshield allowance, so mount on the dash

Nothing in Wisconsin law mentions a dash cam. The phrases "dash cam", "dashboard camera" and "windshield mount" each return no results when searched against the Wisconsin Statutes and against the Wisconsin Administrative Code on the Legislature's document system. That silence is meaningful rather than accidental, because the Legislature did legislate about a camera in a vehicle in exactly one place: Wis. Stat. § 347.446, created by 2025 Wisconsin Act 160, authorizes a school bus to be equipped with a device for recording audio or video of the interior of the bus, but only where the school board or the private, charter or tribal school governing body has adopted a policy, notice has gone to pupils and parents, and the policy is clearly posted inside the bus. Section 347.446(3) then makes those recordings confidential and usable only by school officials and law enforcement. When the equipment chapter wanted to permit a vehicle camera, it said so and hedged it about with conditions. It did nothing similar for private cars.

So the driver is left with two obstruction rules. The administrative one is the stricter of the pair. Trans 305.34(6) opens with a general prohibition, that nothing may be placed or suspended in or on the vehicle or windshield so as to obstruct the driver's clear vision through the windshield, and then adds a flat second sentence barring any posters, stickers or other nontransparent material, other than a certificate or sticker issued by order of a governmental agency, located on the windshield or located between the driver and the windshield. The three carve-outs that follow are exhaustive: an inside rearview mirror attached in accordance with Trans 305.26, windshields tinted by the manufacturer of the glazing as part of original manufacture, and tinting film applied only outside the critical area and above the horizontal line marked "A" by the glass manufacturer. A suction-cup camera body sitting on the glass is nontransparent material located on the windshield, and no paragraph of sub. (6) rescues it.

The statutory rule, Wis. Stat. § 346.88(3), runs on three tracks. Paragraph (a) prohibits driving 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, other than a government-ordered certificate or sticker, which may not cover more than 15 square inches and must sit in the lower left-hand corner of the windshield, the left corner being on the driver's left when seated behind the wheel. Paragraph (b) prohibits driving with any object so placed or suspended in or upon the vehicle as to obstruct the driver's clear view through the front windshield. Paragraph (c) does the same for the rear window unless the vehicle carries an outside rearview mirror meeting Wis. Stat. § 347.40.

The Wisconsin Supreme Court narrowed both of those paragraphs in State v. Houghton, 2015 WI 79, 364 Wis. 2d 234, 868 N.W.2d 143. The annotations printed under § 346.88 record the holdings. On sub. (3)(a), the court reasoned that there was no reason the legislature would ban oil change stickers of one or two square inches while requiring only that the same area be "reasonably" clean under sub. (4), and it read the paragraph to prohibit the attachment of signs, posters and other items of a similar nature to the front windshield. A camera is not an item of a similar nature to a sign or a poster, so paragraph (a) is not the trap for dash cam owners. On sub. (3)(b), the court held that not every object in a driver's clear view is a violation; the paragraph requires a material obstruction, even if a minor one. The practical Wisconsin test for a camera on the glass is therefore materiality, and Houghton construed the statute rather than the administrative rule, which carries no equivalent gloss.

What follows for mounting is specific. Behind the inside rearview mirror is the only position on a Wisconsin windshield that has any support in the rules, because Trans 305.34(6)(a) already accepts the mirror itself and a camera body tucked into its shadow adds nothing the driver was seeing past. A unit stuck low in the driver's sweep is a poor bet on both instruments: Trans 305.05 defines the windshield critical area as the portion normally used by the driver for necessary observations to the front, including the areas normally swept by a factory installed windshield wiper system, and a camera there is squarely in it. A dashboard or vent mount avoids Trans 305.34(6) entirely, since that subsection reaches material on the windshield or between the driver and the windshield, and leaves only the § 346.88(3)(b) materiality question. Cables should be routed along the headliner and A-pillar rather than strung across the glass, since a suspended cord is an object suspended in or upon the vehicle for purposes of paragraph (b).

A Trans 305.34 violation is punished under Wis. Admin. Code § Trans 305.04, which sets the penalty by reference to Wis. Stat. § 110.075(7): a forfeiture of not less than $10 nor more than $200 unless another statute provides otherwise. Trans 305.03 supplies the duty, providing that no person may operate or allow to be operated on Wisconsin highways any vehicle subject to the chapter that is not in conformity with it, so the registered owner is exposed as well as the driver. A charge under Wis. Stat. § 346.88 carries its own scale: Wis. Stat. § 346.95(1) sets a forfeiture of not less than $20 nor more than $40 for a first offense and not less than $50 nor more than $100 for a 2nd or subsequent conviction within a year.

How the violation surfaces matters in Wisconsin, because there is no periodic safety inspection for passenger cars to catch it. Wis. Stat. § 110.075(2) provides that when directed by any traffic officer or motor vehicle inspector the operator of any motor vehicle shall stop and submit the vehicle to inspection, with glass and mirrors named among the items examined, and § 110.075(5) allows a repair order the owner or driver must then satisfy. Against that, Wis. Stat. § 349.02(2)(a) provides that an officer may not stop or inspect a vehicle solely to determine compliance with chapters 341 to 346 without reasonable cause to believe a violation has been committed, though it does not limit issuing a citation for a violation observed during a stop made for a lawful purpose, and it does not apply to a traffic officer or motor vehicle inspector performing duties under § 110.075(2). Because § 346.88 sits in chapter 346, a stop made solely over a windshield-mounted camera needs that reasonable cause, and Houghton's materiality requirement is what the cause has to be about.