So what you're saying is that deaf people should never go cycling?

I ride with an iPod and as Bootlegger says, it's still very easy to hear traffic noise.

Most cars do fine with windows wound up and a loud stereo playing. They don't hear the surrounding traffic at all. Obviously we're more vulnerable but if we're riding predictably we shouldn't be at any greater danger.

I don't think anyone operating a vehicle of any kind on a public road should play their music too loud as it certainly does affect concentration but when I'm on the road I want music.

The bottom line is, if you think it's dangerous, don't do it. If you want music while you ride, take the extra precautions that your choice requires.