In the U. S., the EPA specifies dB limits on exhaust noise. 84dB, I believe, but I&#x27;d have to look it up to be sure (IIRC, 84dB is what&#x27;s stamped on my stock exhaust). There are local limits as well. The limits just aren&#x27;t enforced as a primary offense unless the cop really just uses it as an excuse to check for DUI.<p>It would be a nice start if national parks started turning them away at the gate, as Glacier NP has talked about doing. I&#x27;ll laugh my ass off when I see Harley and Harley-wannabe riders doing u-turns at national park entrances.