Why do bridges freeze before roads in cold weather?

Why do bridges freeze before roads in cold weather?

• A. Bridges freeze first because they are shaded by trees
• B. Cold air circulates above and below the bridge
• C. Bridges have more surface area for ice to form
• D. Road salt is applied more heavily on roads than bridges

Answer: (B)

Bridges freeze first because they’re exposed to cold air on both the top and the bottom, so they lose heat much faster. A road sits on the ground, which provides warmth from the earth, so the surface stays above freezing longer even when air temperatures are cold. The bridge, with air flowing around it and no nearby ground heat to share, cools quickly and ice can form earlier. Other factors like shade, surface area, or how much salt is used can affect conditions, but the rapid heat loss from exposure to cold air is the main reason.

Bridges freeze first because they’re exposed to cold air on both the top and the bottom, so they lose heat much faster. A road sits on the ground, which provides warmth from the earth, so the surface stays above freezing longer even when air temperatures are cold. The bridge, with air flowing around it and no nearby ground heat to share, cools quickly and ice can form earlier. Other factors like shade, surface area, or how much salt is used can affect conditions, but the rapid heat loss from exposure to cold air is the main reason.