black ice
noun phrase

- a dangerous type of ice on roads which is so thin that it cannot be seen by a driver

(Cambridge Advanced Learner's Dictionary)

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WORD ORIGIN

Black ice, also known as "glare ice" or "clear ice," refers to a thin coating of ice on a surface, usually a roadway. While not truly black, it is transparent, allowing the black asphalt roadway to be seen through it, hence the term. It is unusually slick compared to other forms of roadway ice.

Black ice is transparent because it contains relatively little trapped air in the form of bubbles. In addition, it often is interleaved with wet road, which is identical in appearance. For this reason it is especially hazardous when driving or walking because it is both hard to see and unexpectedly slick. Riding bicycles, scooters, or motorbikes on black ice particularly dangerous.

Beware in particular of bridges and overpasses. Black ice forms first on bridges and overpasses because air can circulate both above and below the surface of the elevated roadway, causing the road temperature to drop more rapidly. This is often indicated with "Bridge May Be Icy" warning signs.

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COMMON ICY PHRASES

- cold as ice = s/o having no feelings
- s/he could sell ice to Eskimos = highly persuasive
- be walking/skating on thin ice = in a risky or dangerous situation
- be on ice = nervously waiting
- put (someone or something) on ice = to delay or cancel
- break the ice = warm up the start of a conversation or meeting
- cut no ice with (someone) = not impress s/o
- keep (someone) on ice = keep s/o waiting

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Practice OWAD in a conversation:

"I'm looking forward to the day when heated roadways make BLACK ICE a thing of the past."