You have always heard and possibly seen the signs that say “Bridges freeze before road surfaces” by why do bridges and overpasses freeze first?
As the air temperature falls both roads and bridges will begin to cool. Roads cool slower than bridges because roads can only cool from one side while bridges cool on all sides. The fact that bridges cool from all sides allow the temperature to reach 32 degrees faster than the roads. The next time you come across a bridge or an overpass know that they lose heat much faster than the road and ice could be present while the road is fine.