Why do bridges ice over before roads on solid ground? Unlike a road on solid ground, a bridge is surrounded by air on both sides (top and bottom). All roads lose heat (energy) during cold weather, but a bridge, being surrounded by cold air on both sides, can lose more heat more quickly. As a result, bridges will develop ice before roads on solid ground. Thus the importance of taking bridges seriously during cold weather. Even if the road is wet and not icy, moving from a road to a bridge can be quite dangerous if one is not careful.
My children are still a few years away from learning how to drive (scary!), but warning your children at a young age of the importance of driving carefully across bridges during cold weather is a god life lesson to learn early in life.