The Police has some of the best Bikes out there! But they also have silencers on their exhausts.
@Dotty, yes the engine does change the sound but the exhaust plays a main part in the loud noise that comes out in this debate.
I agree 100% with being noticed but unfortunatly some car drivers are in such a world of their own that they do not hear the loud noise, the bright lights and the flouresents ... I only wish push bikers would put this much effort into their own saftey, I often see them in dark clothes no lights and late at night, I dont but luckily I have always managed to see the shadow of their outline just about to avoid them so far.
And for the origianl question, if your car exhaust FAILS its MoT it is illegal, that is not to do with the sound it makes but to do with the fact it either has holes in it, rusted away, or the brackets have broken and it is falling off .. that is not to do with a loud but in good condition exhaust you cannot compare the two, one is broken and loud, the other is fixed and loud.