Pete wrote:Dave, mirrors work 24/7. Necks only when you turn them (you'd have to know that you needed to turn behind - and same time risk a nose-to-tail)
You only need to check behind when you're planning to deviate from normal travel. In over 30 years of cycling I've not found it neccessary to check behind me every 15 seconds, I don't know why you feel it makes you any safer. It doesn't take that long to check behind, any competent cyclist can do it quite well without a mirror. Also has the benefit of communicating intent to anyone behind you, something that doesn't happen with looking in a mirror.
We've been over this ground too many times. I'm happy it works for you but please stop inferring that they make you any safer than not using mirrors; you've no evidence for it.