Radar Detectors in Missouri: Legal in Cars, Banned in Commercial Trucks

The negative here is provable rather than assumed. The Revisor of Statutes runs a full-text index over the entire Revised Statutes of Missouri, and the queries that would have to hit if a ban existed come back empty: radar detector returns no matches, detection device returns no matches, speed detection device returns no matches, and lidar returns no matches. The word detector appears in exactly one section, Section 376.782, on mammography coverage, and radar appears in exactly one, Section 137.078, which sets depreciation schedules for broadcasting equipment. Chapter 307, the vehicle equipment chapter that regulates lamps, mirrors, mufflers, studded tires and sun-screening film, contains nothing on receivers or detectors of any kind. Missouri therefore has no possession offense, no use offense, no confiscation provision and no separate rule for rental or company cars.

The commercial ban is genuine and it is broader than most drivers expect, because Missouri applied the federal rules to purely in-state trucking. Section 307.400.1 makes it unlawful to operate a commercial motor vehicle as defined in 49 CFR 390.5 unless the vehicle is equipped and operated as required by Parts 390 through 397 of Title 49, and it says so whether the transportation is intrastate or interstate. Part 392 is inside that range, 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, while 392.71(b) forbids a motor carrier to require or permit a driver to violate it. Note the word contains: an unplugged detector in the sleeper or the glovebox is still a violation. The Department of Public Safety has restated the adoption in its own rule, 11 CSR 30-6.010(1), which requires commercial motor vehicles and trailers to be operated and equipped in compliance with 49 CFR 390 through 397 and 49 CFR 100 through 199.

Which vehicles that catches turns on the 49 CFR 390.5 definition: a gross vehicle weight rating or gross combination weight rating, or actual weight, of 10,001 pounds or more, whichever is greater; or a vehicle designed or used to carry more than 8 passengers for compensation; or more than 15 passengers without compensation; or one carrying placardable hazardous material. Missouri then narrows that for in-state work. Section 307.400.5 disapplies Parts 390 through 397 to commercial motor vehicles operated in intrastate commerce to transport property with a gross vehicle weight rating or gross combination weight rating of twenty-six thousand pounds or less, with the carve-out reversed again for hazmat loads, for vehicles designed to carry sixteen or more passengers including the driver, and for covered farm vehicles hauling placarded hazardous materials. In practical terms a Missouri-only box truck rated at 26,000 pounds or under, hauling ordinary freight, is outside the federal radar detector rule; a tractor-trailer, a Missouri-only truck above 26,000 pounds, and any interstate CMV at 10,001 pounds and up is inside it.

One Missouri detail does constrain where a car driver puts a detector, even though the device itself is lawful. The Highway Patrol's glazing rule for the state safety inspection, 11 CSR 50-2.270, defines the driver's vision area as the area within the normal sweep of the wiper blades above a line measured four inches from the bottom of the windshield, and subsection (5)(C) rejects a vehicle when aftermarket vision reducing material or other conditions that obscure the driver's vision are on the windshield. A suction-cup detector parked in the middle of the wiper sweep is a windshield obstruction on those terms. Mounting low on the dash, below the four-inch line, or high behind the mirror keeps the device out of the defined vision area. Missouri's inspection is biennial and only reaches vehicles that have passed the ten-year period following their model year or exceeded 150,000 miles under Section 307.350.1(1), so many drivers will never be tested on the point.

There is no penalty for a passenger-car driver, because there is no offense to violate. 1(3) a fine of up to one thousand dollars. 3 adds an administrative consequence with more bite than the fine, allowing the vehicle and the driver to be placed out of service when the vehicle is not equipped and operated as the section requires, using the North American Uniform Out-of-Service Criteria adopted by the Commercial Vehicle Safety Alliance and the United States Department of Transportation. 010(2), a vehicle placed out of service may not be operated on public highways until the defect that caused the out-of-service action has been corrected.

71(b) also binds the carrier, a company that lets a driver run with a detector is exposed in its own right at a Missouri roadside inspection.