Since the snow fell, a bollard has been taken out on a side road near here. It was bashed by someone coming the wrong way, that is, it's on the right hand side for the direction of travel of the vehicle that hit it. The main road is clear: well-gritted & lots of traffic to melt the snow. Turn off it, & you immediately hit ungritted roads with just enough traffic to compact the snow into ice, which this afternoon had a nice wet slippery surface.
I didn't see it happen, but I don't need to. Someone coming along the nice clear main road turns left across the bus lane into the side road, & too late, realises that he's going too fast & is sliding across the road while still moving forward . . . . He might even have braked, & made it worse.