Radar detectors: legal in cars, banned in commercial vehicles

Wisconsin has never enacted a radar detector prohibition for ordinary drivers. A full-text search of the Legislature's own document system for the phrase "radar detector", restricted to the Statutes and then to the Administrative Code, returns no results in either body of law. That is not an argument from silence about a subject the Legislature never considered: 1995 Assembly Bill 700, introduced by Representatives Musser and Lehman with Senator Burke, was captioned as relating to prohibiting the use and sale of radar detectors for motor vehicles, and it would have made the presence of an operative radar detector in a motor vehicle unlawful and covered radar detection jamming devices as well, with a carve-out for devices used by law enforcement. The bill was not enacted, and the subject was raised again only in passing in 2001 Assembly Bill 896. Wisconsin's statute books record the proposal and not the prohibition.

The restrictions that do exist come from the commercial side. Wis. Admin. Code § Trans 325.02 adopts a list of federal motor carrier safety regulations and directs that they be enforced in Wisconsin in relation to the carriers, drivers and vehicles they reach in the same manner as though the regulations were set out in full in the chapter. Subsection (3) adopts Title 49, Code of Federal Regulations, part 392, and 49 CFR 392.71(a) provides that no driver shall use a radar detector in a commercial motor vehicle, or operate a commercial motor vehicle that is equipped with or contains any radar detector; 49 CFR 392.71(b) adds that no motor carrier shall require or permit a driver to violate that paragraph. Possession is enough, so a detector left switched off in the sleeper of a Wisconsin-plated tractor is already a violation.

Wisconsin routes the enforcement of the adopted part 392 through a different door than it uses for equipment defects. Trans 325.05(2) states that the provisions adopted in Trans 325.02(2), (3), (5) and (7), which are 49 CFR parts 391, 392, 395 and 397, shall be enforced under Wis. Stat. ch. 194, the motor carrier chapter, rather than under the roadside inspection statute.

The other half of the Wisconsin picture is what the police may do rather than what the driver may carry. Wis. Stat. § 349.02(3)(a) defines photo radar speed detection as the detection of a vehicle's speed by use of a radar device combined with photographic identification of the vehicle, and § 349.02(3)(b) provides that the state and local authorities may not use photo radar speed detection to determine compliance with any speed restriction imposed by Wis. Stat. §§ 346.57, 346.58, 346.59, 346.595 or 349.11 or a local ordinance in conformity with them. Wisconsin therefore has no automated speed camera program at all, and every speeding citation in the state comes from an officer working a hand-held or vehicle-mounted unit. The annotations printed under § 346.57 record that Wisconsin courts take judicial notice of the reliability of the underlying principles of radar and apply a prima facie presumption of accuracy to stationary radar devices.

How the detector is mounted is a separate question from whether it may be carried, and this is where Wisconsin drivers get caught. A suction-cup detector stuck to the glass runs into Wis. Admin. Code § Trans 305.34(6), which allows nothing on or between the driver and the windshield except an inside rearview mirror fitted under Trans 305.26, factory tinted glazing and film above the manufacturer's "A" mark, and into Wis. Stat. § 346.88(3)(b), which bars 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. A dash-mounted or vent-mounted detector avoids both.

There is no forfeiture to impose on a private motorist, because there is no Wisconsin offence of possessing or using a radar detector in a car. The device is not prohibited equipment under Wis. Stat. § 347.03, and it appears nowhere in the equipment standards of Wis. Admin. Code ch. Trans 305, so an officer has no basis to cite for the detector itself or to order it removed under the repair-order power in Wis. Stat. § 110.075(5).

For a commercial driver the position reverses. Because Trans 325.05(2) routes the adopted 49 CFR part 392 into Wis. Stat. ch. 194, the penalty is the one in Wis. Stat. § 194.17: a person who violates rules issued by the secretary shall forfeit not less than $50 nor more than $100, and each violation constitutes a separate offense. Section 194.17 also provides that the act or omission of an officer, agent, servant or other person employed by a carrier and acting within the scope of employment is deemed to be the act of the carrier, which is how a driver's detector becomes the company's problem. Wis. Admin. Code § Trans 325.09 provides that no demerit points may be assessed for violations of the regulations adopted in that chapter, so a part 392 forfeiture does not put points on a Wisconsin licence. A driver found with a detector during a roadside inspection can also be placed out of service under the North American Standard Out-of-Service Criteria adopted by Trans 325.02(8).

Mounting violations are enforced independently. A windshield-mounted detector charged under Wis. Stat. § 346.88(3)(b) sits inside chapter 346, so Wis. Stat. § 349.02(2)(a) applies: an officer may not stop or inspect a vehicle solely to determine compliance with that chapter without reasonable cause to believe a violation has been committed.