Jefferson County, MO Noise Ordinances: Vehicle Noise (2026)

Jefferson County regulates vehicle noise through two sections of Title III, the Jefferson County Traffic Code, adopted by Ord. No. 10-0269 on July 7, 2010. 100 bans muffler cutouts outright: no motor vehicle exhaust pipe may carry a cutout or opening between the motor and muffler unless it is completely closed and disconnected from its operating lever so it cannot open while the vehicle is moving. The same section requires every motor to be fitted with a muffler built to quiet exhaust noise as completely as a modern gas-engine passenger car achieves.

110, carried over from the County's May 2, 2009 traffic order, separately bars driving any vehicle in a manner that produces excessive and unnecessary noise from its machinery, motor, signaling device, tires or other parts, or from an improperly loaded cargo. 130 Engine Compression Brakes, prohibits using engine compression brakes in any area the County has posted with signs marking the start of a no-engine-brake zone; the ban does not reach unposted roads. 020 limits the Traffic Code's scope to the part of Jefferson County outside the incorporated cities, these noise rules govern unincorporated county roadways only; Arnold, Festus, De Soto, Hillsboro and the County's other cities enforce their own municipal noise and muffler ordinances on their own streets. Violations of the Traffic Code are misdemeanors enforced by the Jefferson County Sheriff's Department.