Originally Posted by
spare_wheel
I think mirror use can be helpful in some circumstances. Nevertheless, your claim that a mirror would increase my "situational awareness" is amusing. IMO, those who argue that mirrors are always helpful simply do not have much experience riding in dense urban traffic and are extrapolating from multi-lane high speed roads with clear sight lines (eg ex-, sub- and sprawl-urban street design).
I agree with part of what you say.
The claim that mirrors increase situational awareness and/or do so in a way that enhances your safety can't be logically supported in all cases. I think your example of dense urban traffic is a good one. In that kind of traffic I'm heads down, keeping up a good pace, and watching what's in front of me, knowing that I can't do much about what's behind me anyway and best protect my safety by following a good and predictable line.
Nevertheless, I find mirrors improving my safety by enhancing situational awareness on less crowded streets with little traffic. I love to ride on such streets if I can (my commute is 20 miles instead of 15 miles for that reason). On those kinds of roads I like to let my guard down some. I may move significantly further into the lane than I otherwise would, but maintaining some awareness of an approaching car coming up behind me by using my mirror. It is true that on a quiet road like that you can use your ears too. But for me at least I know I often spot a car long before I can hear them. I would rather move out of the way casually than urgently.