Whether you promote or oppose loud cars, it’s always best to know the law regarding vehicle modifications. Every state has laws regulating muffler installation, vehicle modifications, and excessive noise. However, the details of these laws vary by state. This article will give an overview of muffler requirements, modification prohibitions, and general sound limits for vehicles.
Generally, all manufactured vehicles come with a muffler installed to the vehicle’s exhaust pipe. These exhaust systems are intended to reduce fumes, smoke, and noise.
Every state requires a properly installed muffler for any vehicle driven on a public road or highway. These laws generally prohibit the use of a cutoff (the exhaust pipe is cut off before reaching the muffler) or a bypass (the exhaust pipe has an opening allowing the exhaust to bypass the muffler). Since police enforcement is discretionary, citations usually result only when the excessive noise or exhaust is noticeable.
After-market mufflers that promote higher vehicle performance are readily available. However, many states prohibit the sale, installation, or use of any muffler that increases exhaust noise. For instance, in Hawaii, the prohibition includes any muffler that “noticeably increases the noise emitted by a motor vehicle” above factory equipment. Other states prohibit any exhaust system that produces a certain decibel level of noise. For example, in California, exhaust systems that produce more than 95 decibels are illegal.
Aside from noise limitations, some states also prohibit aftermarket exhaust systems that release excessive fumes or smoke into the atmosphere. Most states require periodic emissions tests for vehicles to ensure compliance with the standards.
Generally, an unlawful exhaust modification can result in a fine of $25 to $500. These are usually non-criminal, non-moving violations that will not result in jail time or license suspension. However, failing to remedy the problem can result in increased fines and penalties.
Some states additionally have rules placing limits on the loudness of a vehicle’s radio or stereo. For example, Georgia prohibits any system that can be clearly heard from over 100 feet away. The types of noise prohibitions generally apply only to stereos and radios and do not include horns or other warning systems.