Maryland Radar Detectors: Legal in Cars, Banned in Trucks

Maryland regulates driver equipment by enumeration rather than by general prohibition. Title 22 of the Transportation Article runs through lighting in Subtitle 2 (§§ 22-201 to 22-232), other equipment in Subtitle 4 (§§ 22-401 to 22-421, covering horns, mufflers, mirrors, windshield material, tires, warning devices, seat belts, television-type receiving equipment, airbags and electric bicycle labels) and noise abatement in Subtitle 6. Nothing in that list touches a device that receives a police radar or lidar signal. Because § 22-101(a)(1)(iii) makes the offence "equipped in any manner in violation of this title", an accessory the title never mentions is not an equipment offence in Maryland, and § 22-101(b)(1) says so directly: nothing in the title is to be construed to prohibit the use of additional parts and accessories not inconsistent with its provisions.

The commercial ban is real and it is Maryland law, not merely federal law. COMAR 11.21.01.02 incorporates the federal motor carrier safety regulations at 49 CFR 40, 382, 383, 387, 390 to 393, 384, 395 to 399 and 1572 by reference, and COMAR 11.21.01.07 states without qualification that "49 CFR 392 is incorporated by reference with no amendments or exemptions." Part 392 includes § 392.71, which 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, and that no motor carrier shall require or permit a driver to violate that rule. COMAR 11.21.01.03A applies the incorporated regulations to all trucks, truck tractors, trailers, semitrailers, pole trailers, converter dollies, combination vehicles and buses with a gross vehicle weight rating or gross combination weight rating of 10,001 pounds or more, and 11.21.01.03B extends them to all interstate carriers and to intrastate carriers hauling placardable hazardous materials or operating a vehicle designed to carry 16 or more passengers including the driver.

Where the detector sits is a separate question with its own Maryland answer. Section 22-404(a)(1) forbids driving with any sign, poster, card, sticker or other nontransparent material on the front windshield, sidewings or side or rear windows, and the exceptions in § 22-404(b) define the only compliant windshield zones: above the AS1 line or not lower than 5 inches from the top, whichever is less, and a 7 inch square area in the lower corner, in each case placed so as not to interfere with the driver’s clear view of traffic. A suction-cup detector parked in the middle of the glass falls outside both zones. Section 22-101(b)(3) adds a separate prohibition on operating equipment intended for off-road use while driving on a highway.

A detector does nothing about the enforcement Maryland actually leans on. Section 21-809 defines a speed monitoring system as a device producing recorded images of vehicles travelling at least 12 miles per hour above the posted limit, and a recorded violation is a civil penalty billed to the registered owner rather than a roadside stop. The current penalty ladder under § 21-809(c)(2)(i) runs $40 for 12 to 15 miles per hour over, $70 for 16 to 19, $120 for 20 to 29, $230 for 30 to 39 and $425 at 40 or more, with a $40 cap for violations recorded on Interstate 83 or Interstate 695 in Baltimore County. Under § 21-809(g), if the civil penalty is neither paid nor contested the Motor Vehicle Administration may refuse to register or reregister the cited vehicle.

There is no Maryland offence, and no fine, for owning, carrying or using a radar or laser detector in a private passenger vehicle, because no section of Title 22 creates one. Two adjacent things can still get you cited. Mounting the unit outside the permitted windshield zones is a violation of § 22-404, which like other Maryland Vehicle Law violations is a misdemeanour under § 27-101(a) carrying a fine of up to $500 under § 27-101(b), and can draw a safety equipment repair order under § 23-105 requiring correction within 10 days, with registration suspension if the order is not satisfied within 30 days.

07, prohibits both using a detector in a commercial motor vehicle and operating one that merely contains a detector, and puts a parallel duty on the motor carrier not to require or permit it. 07 adopts Part 392 with no amendments or exemptions.