Re: ipod safety.

When commuting I always listen to an iPod with both ears and actually think I hear road noise better. I use Sony headphones similar to these:

I find that the reduced wind noise across my ears helps me hear traffic sounds better, I can absolutely hear traffic sounds better at speed with the headphones on and the ipod paused then with no headphones. I usually pause the audio for high speed descents as the wind noise obscures the sound enough that I have to rewind when I get to the bottom of the hill so i just pause it. I also listen exclusively to spoken word podcasts and I find that voices are not in the same frequency range as traffic sounds. Traffic sounds tend to be above and below the frequency of voice and with the additional help of my helmet-mounted mirror, I don't recall ever being surprised by traffic from any direction.