[oldcynic]

It's a myth. They will prevent some accidents with pedestrians or bicycles in town because they haven't looked properly. That accident won't kill you anyway.

A loud pipe will make bugger all difference when you're doing 50+ down a major road and that idiot in the 4x4 on the side road junction looks right at you, then pulls out anyway. He probably has music on so gets little input, and no direction, from your nice open pipe.

What saves lives there is the biker actively moving across driver field of vision - eg weave in lane or more dramatic if you think he's going anyway. More motorcycle awareness on the car test might help, but that's not politically popular.

[Gracana]

It's especially noticeable on the highway. A loud bike or car can be heard when it's in front of you, but if it's behind you it is practically silent, and that's the time when it would be useful to notice it.

[Clubber]

Loud pipes create visibility (audibility?) when you are side by side with a driver, or in their blind spot. It reduces the chance of them from mindlessly swerving into your lane.

People usually get clobbered by cars pulling out in front of them, or getting swerved into from the side.

[kingofhdds]

You contradict yourself, I believe. Rider vs pedestrian can cause fatal injuries to both actually. Most likely to a pedestrian, of course, but it's still a human life, isn't it?

[oldcynic]

I understand, at least according to numerous speed campaigns by govt here, that accidents at speeds of 30mph or less are unlikely to kill. As speed limits in town are 30 with some areas 20mph, risk of death to either is low.