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Idaho Statutes
Idaho Statutes are updated to the website July 1 following the legislative session.
MOTOR VEHICLES
CHAPTER 9
VEHICLE EQUIPMENT
49-937. Mufflers — prevention of noise. (1) Every motor vehicle shall at all times be equipped with a muffler in good working order and in constant operation to prevent excessive or unusual noise and annoying smoke, and no person shall use a muffler cut-out, bypass, or similar device on a motor vehicle on a highway. When any motor vehicle was originally equipped with a noise-suppressing system or when any motor vehicle is required by law or regulation of this state or the federal government to have a noise-suppressing system, that system shall be maintained in good working order. No person shall disconnect any part of that system except temporarily in order to make repairs, replacements or adjustments, and no person shall modify or alter that system or its operation in any manner, except to conform to the manufacturer’s specifications. No person shall knowingly operate and no owner shall knowingly cause or permit to be operated any motor vehicle originally equipped or required by any law or regulation of the state or the federal government to be equipped with a noise-suppressing system while any part of that system is disconnected or while that system or its operation is modified or altered in any manner, except to conform to the manufacturer’s specifications.
(2) The engine and power mechanism of every motor vehicle shall be so equipped and adjusted as to prevent the escape of excessive fumes or smoke.
(3) No person shall modify the exhaust system of a motor vehicle or a motorcycle in a manner that will amplify or increase the noise of the vehicle or motorcycle above that emitted by the muffler originally installed on the vehicle by the manufacturer.
(4) A showing that the sound made by a passenger motor vehicle or motorcycle exceeds the maximum allowable decibel level shall be prima facie evidence of a violation of subsection (1) of this section.
(5) No person shall sell, offer for sale, or install any noise-suppressing system or device that will produce excessive or unusual noise.
(6) The driver of a commercial vehicle that is in compliance with the provisions of subsection (1) of this section may allow such vehicle to idle for the purpose of using the vehicle’s heating or air conditioning system as long as the driver is parked for the purposes of resting or sleeping. The provisions of this subsection shall include the use of auxiliary power units to provide heating or air conditioning to the vehicle.
(7) A commercial vehicle that is in compliance with the provisions of subsection (1) of this section and that is refrigerated while parked shall not be prohibited to operate while laden with perishable commodities, pharmaceuticals, or both.
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