When temperatures drop, drivers should beware not only of black ice but of frozen bridge roadways, as bridges freeze before roads in freezing winter weather conditions. 

Roads can withstand freezing temperatures longer due to warm air trapped underneath the surface. At the same time, bridge roadways are exposed on all sides as the structure's top, bottom, and sides are exposed to the freezing air.

Additionally, asphalt roads trap heat from the warmer ground below, while bridges, for the most part, are made from concrete and steel, which freeze faster.

So, while the rest of the road may still be clear, drivers crossing a bridge during a drop in temperature should exercise more caution and avoid braking, changing lanes, or accelerating while driving on the bridge to avoid sliding on newly formed ice on the bridge's roadway.