Sun Prairie, WI Noise Ordinances: Vehicle Noise (2026)
Key Facts
- Compression brake use
- Banned citywide except imminent danger
- Emergency vehicles
- Exempt from the brake ban
- Horn duration limit
- 3 seconds per 1-minute period
- Exhaust requirement
- Must run through an effective muffler
- Compression brake ordinance
- Ord. 2003-115
- First offense penalty
- $5-$500 forfeiture
Summary
Sun Prairie bans engaged compression (Jake) brakes citywide, caps horn use at three seconds, and requires every vehicle exhaust to run through a muffler that prevents loud or explosive noise, under Code Sections 8.32.020 and 10.08.180.
A.Horns—Signaling Devices. The sounding of any horn or signaling device on any automobile, motorcycle or other vehicle on any street or public place in the city for longer than three seconds in any period of one minute or less, except as a danger warning; the creation of any unreasonable loud or harsh sound by means of any signaling device and the sounding of any plainly audible device for an unnecessary and unreasonable period of time; the use of any signaling device except one operated by hand or electricity; the use of any horn, whistle or other device operated by engine exhaust and the use of any signaling device when traffic is for any reason held up. ... F.Exhausts. The discharge into the open air of the exhaust of any steam engine, stationary internal combustion engine or motor boat except through a muffler or other device which will effectively prevent loud or explosive noises therefrom.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 71).
Full Breakdown
020(A) limits horns and signaling devices: sounding any horn or signaling device on an automobile, motorcycle or other vehicle for longer than three seconds within any one-minute period is a violation except as a danger warning, along with unreasonably loud or harsh signal sounds, signals operated other than by hand or electricity, and any horn or whistle operated by engine exhaust. Subsection F targets exhausts directly, making it a violation to discharge the exhaust of a stationary internal combustion engine, steam engine or motor boat into the open air except through a muffler or other device that effectively prevents loud or explosive noises.
180: defined to include Jake brakes, Jacobs brakes, engine brakes and dynamic braking devices that convert a truck engine into an air compressor for braking without wheel brakes, operating a motor vehicle with a compression brake engaged within city limits is unlawful except to avert imminent danger. Emergency vehicles are exempt from the compression brake ban under subsection C. 08.
Violations & Fines
Horn and exhaust violations under Section 8.32.020 fall under the general penalty of Section 1.24.010, forfeiting five to five hundred dollars on a first offense and twenty to one thousand dollars for a repeat within a year. Section 10.08.180 does not print its own separate fine, so a compression brake violation is likewise punished under Section 1.24.010's general penalty schedule, with each violation treated separately.
Frequently Asked Questions
Are Jake brakes illegal in Sun Prairie?
How long can I honk my horn in Sun Prairie?
Does Sun Prairie require a muffler on vehicle exhaust?
Sources & Official References
Other rules in Sun Prairie
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Vehicle Noise in Nearby Cities
How other cities in Dane County handle vehicle noise.