Montana Title 61. Motor Vehicles § 61-9-435. Exhaust noise limitation

(1) Except as provided in subsection (3), a person may not operate a motor vehicle with an exhaust system that emits a noise in excess of 95 decibels, as measured by the society of automotive engineers' standard j1169 (May 1998).

(2) A person charged with violating this section may not be convicted if the person had reasonable grounds to believe that the vehicle was not operated in violation of the standard in subsection (1).

(3) This section does not apply to a motorcycle or quadricycle that is subject to 61-9-418.