just 'cause the majority of respondents use mirrors doesn't mean the majority of roadies use mirrors. probably, the over 50 set is more likely to use one. I personally don't use one. I rely on actually looking, despite my arthritic neck. I was riding with a guy last year, and we needed to go left. he glanced in his mirror and swerved across the lane, right in front of a car. he made it, barely. I especially wouldn't use one, after that episode, even though it was a case of him being a guy that only rides twice a year (and drives everywhere with his bike rack on his car, which could be the subject for a whole new thread here). As for using your ears, I think we all use that as a preliminary sense as to whether to expect to see a car back there, just don't decide to swing across the lane (because you don't hear anything behind you), and get hit by a hybrid running on batteries. or a quiet scooter.