Interesting, I had a look and it seems like it should be limited to 80dB for the biggest motorcycles. But that's when measuring in specific conditions in a lab, so there's a more "practical" (ahem) limit that depends on the model but is always at harmful levels (>80dB) and is measured when the engine is only at 50% of its maximum power.
So we have a badly designed law which is, as you mentioned, not even enforced. Sounds like France indeed.
I've looked a bit into it, and it's actually not that bad. [0] is a French source (not government affiliated).
Basically, as you said, there's the "official" test, which is dynamic (the bike has to be moving) and involved enough to not be practical for everyday controls by police.
But there's also a "static" test, for the purpose of facilitating police controls. The meat of it, from the article, is below. The parameters for this test are given on the registration slip of the vehicle (expected sound level / RPM).
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The sound should be measured with a microphone placed as follows:
* At an angle of 45º to the vehicle's longitudinal axis
* At 50 cm from the muffler
* At the height of the highest point of the muffler and at least at 20 cm from the ground
* If the bike has mufflers on both sides, testing should be done with two microphones, one on each side
Testing conditions:
* Testing must be done at 50% of the nominal power RPM [not max RPM]
* If max RPM is 5000 or less, testing must be done at 75 % of nominal power RPM
* There must be at least 3m of free space around all sides of the vehicle
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This level is higher than the one in the official test, but it doesn't really mean anything. The official test is done wide open throttle starting at 50 km/h, so it should reflect fairly well the actual noise produced when riding around town. The static test isn't involved in the homologation of the vehicle, it's just there for the police to be able to check that the vehicle hasn't been tampered with.
Thanks for clarifying. Given the considerable amount of motorcycles that are way too loud, it still feels like the noise limits for homologation are way too high. Or if that many bikes have been tampered with, it means there really is absolutely no enforcement whatsoever. Either way it sucks :/
I would have thought French have a more strict approach given how they throttle performance of bikes. Like a hayabusha with 100 HP. I think a while back max. performance was 100HP for bikes.
Well, as always, there's the theory, and then there's the practice.
The 100 HP law has been removed around 2016 because the EU said it was it against free trade in the block. I'm not really sure how that works and if a vehicle must only comply with EU regulations in order to be sold in any and every country. As a biker, I'm happy it was removed. It was just silly and useless. A 100 HP bike, even a heavy one like a Hayabusa is powerful enough to give you a bad day if you have no idea what you're doing [0].
More related to the issue at hand, limiting was very easy to circumvent and practically impossible to verify without putting the bike on a dyno. Older, non fuel injected models only had some kind of mechanical limiting for admission. My bike was limited by the ECU which is trivial to swap. Actually in my particular case it's a bit more involved since the coded key is tied to the ECU, so you'd have to also change the key. The ECU is just a black box with a bunch of connectors. It doesn't say anything as to what it does.
It's more or less the same issue with mufflers. They're pretty trivial to change and even if they're sold as street legal, it's very easy to remove a capsule to "open" it up.
However, this is much easier to control than the ECU mapping. Just put out a mic and measure the sound level. Is it above the value in the registration? It's illegal. Done.
But I think it's just much easier to enforce speed limits. Just set up a speed camera and take pictures of the guys passing by. You don't even have to stop them. And, as a bonus, it counts as "doing something" for traffic safety.
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[0] One good thing in France (and maybe the whole EU, now) is that getting a motorcycle license is not as easy as the car license. But in traffic stats, motorcycles are usually counted in the category of "2 wheelers" (which actually includes some trikes). The issue here is that not everyone has an actual motorcycle license. And, related to the power issue, it would seem that "inappropriate speed" was a factor in more accidents involving small bikes (those not requiring the full motorcycle license) than bigger ones. Below is a (2008) study showing that:
* "small bikers" are more often the cause of the accident than "big" ones.
* big bikes, when the cause of the accident was a "loss of control", were on average going 15 km/h above the posted speed limit. Pretty much any 100 HP motorcycle can go above 145 km/h (highway speed limit is 130).
So we have a badly designed law which is, as you mentioned, not even enforced. Sounds like France indeed.