Hey Lifehacker. I often see Harley motorcyles riding by with really loud exhausts and not getting pulled over. But I frequently see people in hotted-up cars that are much quieter getting fined for having a loud exhaust. Are the laws regarding exhaust noise levels different for cars and motorcycles? Thanks, Two Wheels
Bike exhaust picture from Shutterstock
They are indeed. The laws surrounding exhaust noise are covered by Australia's Motor Vehicle Standards Act. This defines the limits on the external decibel level of vehicles in order to reduce noise pollution in the community.
The rules and regulations are divided into separate categories depending on the size of the vehicle. For example, passenger vehicles including cars fall inside "Category M", while two and three wheeled vehicles are classed under "Category L". There are various sub-classes in each category and the maximum exhaust noise is different for each.
All manufacturers must demonstrate that their vehicles meet a specified noise limit during testing before they can be sold on the market. In other words, it's a problem that only arises with poorly maintained engines or heavily modified vehicles.
A degree of tolerance is usually permitted for vehicles that fall outside their category's noise limit, although the amount varies depending on the jurisdiction. Police discretion also plays a pretty large part.
In recent years, the maximum allowable drive-by noise was significantly reduced across all vehicle categories. You can see the current restrictions in the below table:
As you can see, the noise limit is considerably lower for M-Category vehicles than L-Category vehicles. This may explain why you've seen modified cars pulled over by police while noisier motorcycles continue to scream by unmolested. If you want to be obnoxiously loud, bag yourself a chopper -- The Man won't be able to touch you (although the pavement might).
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