Why can bridge surfaces freeze before regular road surfaces?

Bridges can freeze before regular road surfaces primarily because cold air circulates above and below them. Unlike typical roadways that are supported by the ground and retain heat, bridges are elevated structures. This elevation allows cold air to flow freely beneath them, resulting in a quicker drop in temperature. Since they lose heat from both the top and the bottom, bridges can reach freezing temperatures faster than road surfaces that are insulated from cold air on one side.

In contrast, the other factors mentioned do not adequately explain the freezing phenomenon. The color of a bridge's surface or the materials from which it is made do not significantly impact frost formation. Similarly, while sunlight might warm surface areas, it is the circulation of cold air that plays a more decisive role in the freezing process.