[Tosses grenade]Helmets[hides] and less contraversial normal clothes.
Drivers see people on them as more human and capable of error and therfore take more care around them.
Plus they are quite visible bikes.
I think that there's something in this but, extrapolating, is it helped because most people can visualise themselves spending a quid to get a day's use of them?
Conversely, people see a lycra-clad roadie or baggied-up MTBer and they cannot see anything beyond the image, so they don't feel any empathy towards the cyclist.
How about some of the riders themselves being a bit more circumspect if they aren't used to cycling in London?
I wouldn't be surprised if it wasn't many, if not all, of the above reasons to some extent.