CharlieB said:
Is there any advantage to rear view mirrors in a busy commute, please?
Bar mounted/helmet mounted?
Any users?
Asked myself the same question a while back, then realised it was for the same reason as Sheepy.
I would suggest, if you can, to change your riding style and take more "life saver" looks.
I'm not be "purist" here (I have nothing against mirrors), I just think that the communication that a cyclist provides by looking back at a car/vehicle is far more important than the benefit of glancing in a mirror to plan your move (especially given the blind spot issue that mikey mentions). I think it is far better to just "get used" to looking back really, really often (which is tricky at first).
On a motorcycle you are trained to look in your mirror every 20 seconds or so (at least I was) thats a lot of "rear looking" for a cyclist, but you get the idea.
If it helps, I once filmed my whole ride into work and posted it for "self improvement"

...I got tons of suggestions from the forum on how to adjust my riding style (many of which I have adopted, some I have ignored) but it took a pal (who doesnt ride) to notice that i didnt look back enough.....
I do now...it is sooooo important
PS Mirrors "stick out" quite a bit and cause issues when filtering on a really busy commute as well.