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

Part 3, Ch. 1, Sec. 1(E) of the Jefferson County Policy Manual requires that no person operate any vehicle in unincorporated Jefferson County that is "not equipped with a muffler in constant operation" (E.1), and bars operating a vehicle whose muffler is not "properly maintained to prevent any noise in excess of the noise emitted when the muffler was originally installed by the manufacturer" (E.2). E.3 separately prohibits muffler modification: no vehicle may run a muffler that has been "equipped or modified with a cutoff, bypass, or any similar device," a provision aimed squarely at aftermarket exhaust cutouts and straight-piped exhausts.

These muffler rules sit alongside the Regulation's numeric vehicle tables in D.1, which cap public-road noise by vehicle type and posted speed, e.g., 80 dB(A) at 35 mph or less for most vehicles and 78 dB(A) flat for vehicles on private property under D.2. A defective or modified muffler that pushes a vehicle over those speed-based tables is a separate, stackable violation from the muffler-equipment requirement itself. Sound is measured under Section C.1-C.2 at 50 feet from the center of the travel lane for a public road or 25 feet from the nearest dwelling for private-property operation.