The wind drowns out more car noise than the ear bud in my experience. I dont wear them if I am traveling in a well traffiked area, but in my neighborhood and the ones around it, I MIGHT have a car pass me 4 times max while I am out riding during the day - and they are going 30 mph.

Trust me - Im the most paranoid person in the world - If there is ANY chance that wearing the one bud would be dangerous, I dont do it.

I DO wear my MP3 player with both buds or use speakers if I am on the trainer.

I just wondered what other people listen to - not where they listen to it