Kauai County, HI Noise Ordinances: Vehicle Noise (2026)

Section 16-17.27 of the Kaua'i Traffic Code targets three separate sources of vehicle noise. First, every motor vehicle operated on a public highway or street must carry a muffler or mufflers of sufficient capacity to stop the escape of excessive, unnecessary or unusually loud noise as well as annoying fumes or smoke; a worn-out or missing muffler is itself the violation. Second, the ordinance bars operating a vehicle whose motor or exhaust system has been altered or modified so the noise it emits becomes excessive, unnecessary or unusually loud, and separately bans dummy mufflers, cut-outs and bypass devices that route exhaust around the muffler entirely; these are the provisions that reach modified straight-pipe and 'cut-out' exhaust setups.

Third, drivers may not accelerate or 'rev-up' an engine on a public highway except under normal or emergency conditions, and revving primarily to make excessive or unusually loud noise is unlawful outright; the ordinance places the burden on the driver to prove the noise happened under normal or emergency conditions rather than on the County to prove otherwise. Kaua'i Police Department officers enforce the section, and violators are subject to the general Traffic Code fine under § 16-21.6, which sends the case to the district court for a fine set under Hawai'i Revised Statutes Chapter 291D rather than a fixed county dollar amount.