Picture in your mind:
100 cars a minute pass a certain part of the road every 1 minute. The temperature is just below freezing. Each car is belching out steam and droplets of water. Black ice everywhere.
Black ice = evil.
As I said before ALL hydrocarbon burning vehicles produce water as a combustion product. The white exhaust you see is WATER (steam). Carbon dioxide is invisible in gaseous form.
That sounds suspiciously racist! ;)
As an ex truck driver I can deal with black ice. However your average 4 wheeler, now thats a another story.