The EPA also considered the issue of "noise visibility" as popularized by the slogan, "loud pipes save lives". This is the theory that a small group of motorcyclists believes that they are making themselves more conspicuous to other motorists in traffic by modifying their motorcycle exhaust systems to produce an excessive level of exhaust noise. The EPA concluded that the proposed noise emissions regulations would have no effect on rider safety. They did however voice their opinion to this "noise visibility" theory;
"Motorcyclists who are depending on the noise generated from their machines to provide a necessary warning to other road users are gambling with their own safety7-1."
Although it may seem obvious that the noise emitted by loud motorcycle exhaust systems would aid in conspicuity and cause more watchful driving by other motorists, in reality there hasn't been a single thoughtful study done that supports this theory. To the contrary, there are several via the Internet that prove otherwise.
Oddly enough, the two types of motorcycles that most often use loud exhaust systems (cruisers and sport bikes) are significantly over represented in crash data (accidents per type of vehicle, per mile)7-2.