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Difficulty: EasyWinter Driving, Snow, and Black Ice

Why do bridges and elevated overpasses typically freeze and become icy before surrounding ground-level roadways during winter weather?

  1. Cold air circulates both above and underneath the bridge deck, losing heat faster than roads insulated by the ground.Answer
  2. B
    Concrete and steel bridge surfaces absorb moisture from vehicle tires at a higher rate than standard asphalt.
  3. C
    Elevated structures attract more atmospheric pressure, which lowers the freezing point of water on the surface.
  4. D
    Bridges are built at a slight incline, allowing melting snow to pool and refreeze quickly in the center lanes.

Answer

Bridges freeze first because cold air circulates both above and underneath the bridge structure, cooling it more rapidly than roads resting on the earth.
Ground-level roads retain heat from the earth beneath them, whereas elevated bridges and overpasses are exposed to freezing air on both their upper and lower surfaces. This dual air exposure causes bridge decks to cool down and freeze much earlier than adjacent roadways.

Step-by-Step Solution

1
Identify the environmental factor affecting elevated road structures.
Bridges lack ground insulation underneath them.
Roadways built directly on the ground benefit from heat stored in the earth below.
2
Analyze how temperature affects exposed surfaces.
Air passes above and below the bridge deck simultaneously.
Dual air exposure accelerates thermal loss, bringing the surface temperature down to freezing faster than adjacent ground roads.

Key Concept

Freezing hazards on bridges and overpasses
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Topics

Winter Driving, Snow, and Black Ice

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