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Why is black ice most likely on bridges and shaded road sections on a cold morning?
- A.Bridges are always salted first so they never freeze
- B.Shade prevents ice from forming
- C.Black ice only forms at noon
- D.Bridges cool from above and below and shaded pavement warms last, so a thin, nearly invisible ice layer forms there first
Correct answer
D. Bridges cool from above and below and shaded pavement warms last, so a thin, nearly invisible ice layer forms there first
Why
A bridge deck loses heat from both surfaces, so it can be icy while the road before it is merely wet. Shaded curves and north-facing slopes hold the same trap, which is why a wet-looking road at near-freezing temperatures deserves suspicion.
Manual topic: Winter Driving - Black Ice · From the General Knowledge practice bank (GK-301).