The thing about black ice is that you can't see it. Still, it was pitch black (0700 this am), and was probably going too quickly for the roundabout given that there was frost & ice (it was above 0 when I left the house). I turned left, the bike didn't & in a second I'd lost it. Luckily (absolutely true) the bus we both slid under had come to a standstill. No injuries other than gravel rash on left elbow & mammoth bruise on left calf. Bike OK, GoreWear jacket torn apart . Seriously folks, take care when its icy, you never can tell when you are going to lose it, & when you do, its unstoppable.