The difference is that they can be identified when in a car and penalised. Perhaps cyclist would get a better image if all bikes had registered owners and prominent registration plates like motorcycles, enabling easy identification and punishment of those who disobey the rules of the road.

I hope you don't mind me commenting on several things you've said, but what do you think of the fact that although Ian has identified the people involved in several incidents when his bike was damaged (sometimes severely) and he was even assaulted (and I was a witness to those handprints on his neck) and yet not *once* has the identification led to punishment.

And yet each year in Cambridge many cyclists get fixed penalty tickets handed out on the spot for pavement cycling and lack of lights.

I do think it would be good if poor cyclist behaviour could be reduced. It gives cyclists a bad name, and makes life much less pleasant on the roads for those of us who do cycle carefully and safely and within the law. But I don't think registration would make any difference.