Is it legal to drive a car with a loud rumbling muffler? No, it is not

Is it legal to drive a car with a loud rumbling muffler? No, it is not

How often have you been sitting at a traffic light – or lounging in your yard – and, long before you can see it, you hear a car approaching? The noise from the exhaust is so loud you would swear it’s a low-flying airplane… or a whole squadron! While car enthusiasts may argue the benefits and/or “coolness factors”, and others may argue it’s not a safety concern, some may wonder, “Is that legal?” And the answer is a resounding, “No. It’s not.”

Oregon law limits how loud a vehicle’s exhaust can be based on the age and type of vehicle. Oregon Revised Statute (ORS) 815.250 requires exhaust systems to “meet noise emission standards determined by the Department of Environmental Quality to be substantially equivalent to the following standards based upon a stationary test conducted at a distance of 25 feet…” Those decibel limits are:

  • Certain vehicles required to establish registration weight and commercial buses manufactured before 1976 – 94 decibels; manufactured in and after 1976 – 91 decibels.
  • Motorcycles and mopeds manufactured before 1976 – 94 decibels; manufactured in 1976 – 91 decibels; manufactured after 1976 – 89 decibels.
  • All other motor vehicles manufactured before 1976 – 92 decibels; manufactured in and after 1976 – 88 decibels.

It’s easy to get caught up in the fog of numbers, as most legislation contains a great deal of “if/then” scenarios that are, quite often, confusing. Additionally, most people – including most police officers – don’t have a decibel meter handy to get an accurate measurement, consistent with DEQ testing standards, to be able to determine the exact decibel level of an exhaust system. So…how are these types of violations enforced?

ORS 815.025 – Causing unreasonable noise with vehicle, addresses vehicle noise, including exhaust levels, by stating, “A person commits the offense of causing unreasonable noise with a vehicle if the person operates upon any highway any motor vehicle so as to cause any greater noise or sound than is reasonably necessary for the proper operation of the vehicle.” This catch-all of a statute can be used to address the noise created by vehicles that have modified exhausts, as well as factory-installed exhausts that allow the user to adjust the exhaust volume through controls inside the vehicle, without having to specify the decibel level. It is worth noting, all vehicle manufacturers are required to certify to the state that their vehicles comply with the exhaust noise limits.

This statute offers a common-sense approach to addressing exhaust, and other, noise by a vehicle. For instance, if two identical 2021 Ford Mustangs were side-by-side, running at generally the same RPMs, and one of them sounds like it’s part of the aforementioned squadron, it’s fairly easy to determine that vehicle is causing “greater noise or sound than is reasonably necessary for the proper operation of the vehicle.” The same comparison can be made between any vehicles of the same year, make, and model.


The Beaverton Police Department is committed to providing a safe city, serving community members with compassion and respect. Traffic education and enforcement are important factors to addressing livability issues within our City.

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