Serving Boone, Blowing Rock, Banner Elk, and other towns of the North Carolina High Country | Founded 05-05-05

January 18, 2007 issue

Black Ice Creates Subtle but Serious Road Hazards

Story by Allison Peacock

One of our most treacherous road hazards is black ice, a very real danger that occurs frequently during the winter and is a “major culprit of auto accidents in the High Country,” according to Boone Director of Public Works Blake Brown.

Two recent accidents—one of them fatal—were attributed to black ice.

The term itselfis slightly misleading, as the ice is in fact transparent. However, because the thin layer of ice forms on dark asphalt, it appears black.

And that’s what creates the problem. Drivers are often unaware that black ice is on the road until they actually drive over it. The road appears merely wet and not frozen. Because the ice is hard to identify without actually touching the road, drivers rarely have any advance warning of its presence.

Black ice forms most commonly when the humidity of the air increases while the temperature of the road decreases. Foggy areas are prime locations for black ice, as the water in the air can quickly freeze to the cold road, according to Brown. Other places that frequently generate black ice conditions are bridges and the shaded areas of roads. In these locations, the road is exposed to colder temperatures, increasing the probability that black ice will form.

Black ice also forms when ice and snow melt during the day on the side of the road and then trickle onto the road surface. This thin coating of water is a good candidate for freezing rapidly into black ice when the temperature drops in the evening.

Black ice can form anywhere, and there is no foolproof way to predict when or where it will appear on the road. It often forms in sporadic patches and occurs frequently during the colder temperatures at night. Black ice can also be more of a hazard in the early morning, as the ice may melt in certain locations when the sun rises, but shaded areas may retain a thin layer of ice.

Drivers should be aware of the dangers and expected locations of black ice. If weather conditions are suspect for black ice conditions, drivers should be even more cautious than usual, even if the road appears fine.

Brown suggested driving carefully at night and when there is a definite “chill in the air.” He added, “You just never know.”