Mirror Mirror when I bike; its the distance that I like.
There are numerous threads about mirrors on BF and someone has surely shared this realization before, but since it just came to me...
I'm a committed mirror user, but on my last commute it was missing so I had to adapt. I am accustomed to turning my head to look behind me; when a car approaches I generally glance back at them, primarily to let them know I see them. Without a mirror, I just glanced back on a 5-10 second basis and I was not surprised by anyone.
On reflection, what I gain with a mirror is a longer period of situational awareness covering a much longer distance that I can achieve without it. With a mirror, my glances inform me about what's cooking 1/4, even 1/2 mile back, whereas without it my awareness distance was only about 200 feet or so.
So I can now clearly articulate that my reason for using a mirror in a commuting context is that it gives me much better situational awareness to the rear.