What is black ice?

Black ice is a thin layer of ice that forms on road surfaces, making it particularly dangerous because it is often nearly indistinguishable from the asphalt underneath. It can appear clear, allowing drivers to see the road's dark color beneath it, hence the term "black" ice. This phenomenon can catch drivers off guard since they might not be aware that the road is actually icy due to the lack of visual cues typically associated with ice, such as white or frosty appearances.

The other options describe different characteristics of ice on roads but do not accurately define black ice. For example, a thick layer of transparent ice would not be classified as black ice, as it would likely be more visible and not pose the same hidden danger. Similarly, visible signs of a frozen road surface would not capture the essence of black ice, which is often imperceptible until it is too late. Lastly, while rain can create slippery surfaces, black ice specifically refers to freezing conditions that produce a thin, transparent layer of ice, which is a distinct condition compared to wet surfaces from rainfall.