King County, WA Noise Ordinances: Vehicle Noise (2026)
Key Facts
- Muffler required
- good working order, constant operation
- Illegal modification
- any device exceeding chapter's sound limits
- Max sound level
- WAC 173-62-030 Table I, at 50 feet
- First violation fine
- up to $125
- Second violation fine
- up to $250
- Enforced by
- King County Sheriff and director
- Geographic reach
- unincorporated King County public highways
Summary
In unincorporated King County it is unlawful to drive, or let anyone else drive, a motor vehicle on public highways without a muffler in good working order and constant operation, under King County Code § 12.86.210. § 12.86.220 goes further, banning any modification or removed muffler that lets a vehicle emit sound above the chapter's limits, backed by civil infractions and sheriff enforcement.
12.86.210 Motor vehicles – mufflers. It is unlawful for any person to operate, or for any owner to permit any person to operate, any motor vehicle upon the public highways which is not equipped with a muffler in good working order and in constant operation. ... 12.86.220 Motor vehicles – modification to motor vehicles. It is unlawful for any person to modify or change any part of a motor vehicle or install any device thereon in any manner that permits sound to be emitted by the motor vehicle in excess of the limits prescribed by this chapter. It is unlawful for any person to remove or render inoperative, or cause to be removed or rendered inoperative, other than for purposes of maintenance, repair or replacement, any muffler or sound-dissipative device on a motor vehicle.
Full Breakdown
240 blocks the sale of new vehicles that exceed the acceleration-test sound levels in WAC 173-62-030's Table III. 600, and either may call on other county departments to assist. 310, but that is a separate provision from the on-highway sections that govern cars and trucks.
Violations & Fines
A first chapter 12.86 violation within 12 months, including an unmuffled or illegally modified vehicle under §§ 12.86.210 and 12.86.220, is a civil infraction under K.C.C. chapter 23.20 punishable by a fine up to $125 under § 12.86.700; a second violation within 12 months rises to up to $250, and each further violation within that window can double the prior fine. § 12.86.710 lets a cited driver appeal, and a documented good-faith mediation attempt can get a first violation dismissed.
Frequently Asked Questions
Is it illegal to drive without a muffler in unincorporated King County?
Can I modify my exhaust for a louder sound?
What's the fine for a loud vehicle in King County?
Can I fight a muffler citation?
Sources & Official References
Other rules in King County
Compare King County to another location·View the Washington noise ordinances overview
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