In reply to Liam M:
> (In reply to AndyC) I'm confused what problem it would be solving. Do you not check behind you before making any change of line? Are other cyclists trying to cycle through you?
99% of the time I know what's going on behind me, but sometimes you can't afford half a second to look back because you're doing 45 kph about 5 m from the car in front.
But an example from this afternoon - straight, flat, two lane road, I'm at the head of about 6 cyclists, approaching a long queue of stationary traffic at about 35 kph. Moved out close to the centre of the road and timed my pull out to overtake the queue with the passing of the last oncoming car. As I was crossing the centre line I found the guy behind had moved up so he was level with my pedal, leaving me almost nowhere to go. I didn't know he'd suddenly changed position because I was concentrating on the traffic ahead and I had assumed too much common sense in the folk behind.
If I'd had a mirror I might have seen what he was up to.