Aren't you thinking of below zero Celsius, not Fahrenheit? And how does the hot exhaust move downward to the pavement? In my experience hot air rises and, when it's really cold, water vapour instantly crystallizes or just vanishes.

In fact, when it's really cold -- like it is in midwinter Winnipeg -- my experience is that black ice was not a problem as there is no water around to form ice though a layer of packed snow can be very slippery. Black ice seems to more of a problem in Toronto where temperatures often flirt with the freezing mark (32F 0C) as there can be water lying about that freezes in a sheet when the temperature drops below freezing. It looks just like water and can be a surprise.

Anyhow, I see you're from Minneapolis and would have thought we had similar experiences but apparently not.

My wife and I headed out on an MUP last January and were very slowly and carefully and studlessly picking our way over areas of "white ice." We were fine until we hit an area where the path sloped down a bit toward the river and then it was an instant unavoidable crash. In fact, I started sliding down toward the water and was relieved when I stopped. It was hard to stand up -- too slippery and not flat -- and hard to shuffle back to dry land. The good thing about ice is that you slide on it when you fall and that, along with layers of clothing, mitigates a lot of injury. Just ask any hockey player.

I'd like to be able to ride in the winter so it's time to buy some studded tires.