Connecticut Protects Radar Detectors by Statute, Except in Commercial Vehicles

The structure of § 14-137(a) is what carries the answer. The section is a general grant of rulemaking authority: the commissioner may make, alter or repeal regulations governing the administration of all statutes relating to motor vehicles, may certify any device or accessory forming part of a motor vehicle or its equipment as compliant with chapter 246, may limit the use of any device or accessory in any way that appears required for safety, may authorise the use of a device on the highway, and may make or repeal regulations about any such device in the interest of public safety. The radar detector proviso is drafted as an exception to all of that. Because it removes the subject from the commissioner’s regulatory power rather than merely declining to ban detectors, a Connecticut driver’s position does not depend on the current contents of the motor vehicle regulations, and it cannot be changed by the department without the General Assembly acting first.

The proviso reaches three activities and one class of vehicle. It covers possession, installation and use, and it applies to a radar detecting device in any motor vehicle. Nothing in the section attaches conditions about mounting position, windshield placement or a driver’s age.

The commercial carve-out comes from a different route entirely, which is why it is easy to miss. CGS § 14-163c(a) authorises the Commissioner of Motor Vehicles to adopt regulations incorporating by reference the standards in 49 CFR Parts 382 to 397, and to apply them to a motor vehicle or motor carrier as defined in 49 CFR Part 390 that is in intrastate commerce with a gross vehicle weight rating, gross combination weight rating, gross vehicle weight or gross combination weight of eighteen thousand one or more pounds; in interstate commerce at ten thousand one or more pounds; designed or used to carry more than eight passengers including the driver for compensation, or more than fifteen passengers including the driver without compensation; or used to transport placarded quantities of hazardous materials. The commissioner exercised that authority. Regs. Conn. State Agencies § 14-163c-1(a) incorporates by reference Parts 382, 383, 384, 385, 386, 387, 388, 390, 391, 392, 393, 395, 396 and 397, each as amended from time to time, and subdivision (10) of that list is Part 392, "Driving of Commercial Motor Vehicles". Inside Part 392, 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, and 392.71(b) forbids a motor carrier from requiring or permitting a driver to violate that. The regulation was last amended, per the eRegulations record, on October 4, 2013.

So Connecticut is a state where the passenger-car answer and the commercial answer come from opposite directions: a statutory bar on the state regulating detectors at all in ordinary vehicles, and a state regulation that pulls the federal commercial prohibition into Connecticut law for vehicles above the weight and passenger thresholds in § 14-163c(a). Both are enforced by the same officials, since § 14-163c also gives police officers and motor vehicle inspectors the powers to enforce the adopted motor carrier safety regulations.

One limit on the proviso is worth noting because the wording is precise. Section 14-137(a) protects a "radar detecting device". A text search of the General Statutes and the 2026 Supplement returns no Connecticut provision addressing a radar or laser jamming device, and the only jamming statute on the books, § 53a-127c, is unrelated to traffic enforcement. Connecticut has therefore legislated about detecting, not about interfering with a police speed-measuring device.

For a passenger vehicle there is nothing to enforce, because the commissioner has no power to write a rule against a detector in the first place. Section 14-137(a) makes a violation of any regulation adopted under that subsection an infraction, which is the penalty attached to the rules the commissioner may make, not to detector use. In a commercial motor vehicle the exposure is real. Because 49 CFR Part 392 is incorporated as a Connecticut regulation by Regs. Conn. State Agencies § 14-163c-1(a)(10), a detector in a covered vehicle is a violation of both the federal rule and the state regulation, reachable at a roadside inspection by police officers and by motor vehicle inspectors under the enforcement powers in CGS § 14-163c.

On the speed-enforcement side, CGS § 14-219c limits how the reading itself may be used: a prima facie presumption of accuracy attaches to a radar, speed monitoring laser, vascar device or other device approved by the Commissioner of Emergency Services and Public Protection only where a competent police officer testifies that the operator had adequate training and experience, that the device was in proper working condition established by proof that the suggested testing methods were followed, that it was used where road conditions provide a minimum possibility of distortion, that the patrol car’s speed was verified if moving radar was used, and that the device was expertly tested within a reasonable time after the arrest by means not relying on its internal calibrations.