The term ‘black ice’ refers to two conditions: a new layer of ice on water, which appears dark in color because the ice is transparent and so we see the deep water below, or as a layer of clear ice on a roadway, which makes for hazardous driving conditions.
In both cases the ice is not black but transparent, and therefore shows the color of the underlying surface.
The ice is clear because no air bubbles are trapped in the ice.
Lots of trapped air makes an object look white. Snow looks white because of air trapped between crystals.
The danger of driving on a road covered with black ice is that the roadway can appear to be merely wet.
Drivers may not recognize the slippery conditions until it is too late.
Crashes also occur when a roadway freezes over quickly because of freezing rain.
A freezing rain situation occurred in the northeast on Jan. 18, resulting in several multiple vehicle pile-ups and some deaths.
The temperature of the road was below freezing, and when rain fell it quickly froze, resulting in extremely hazardous conditions.
Even walking can be seriously affected on certain days.
Keep in mind that your thermometer placed several feet above the ground may register an above-freezing temperature while the temperature at the surface, where ice can form, may be below freezing.
If a sidewalk is covered with clear ice, it will look dark gray — like a wet sidewalk.
This “gray ice” can be hazardous for walking and undoubtedly contributes to thousands of personal injuries during winter.