Clear and Present Danger

Jan. 10, 2020

Black ice is not really black, but perfectly clear ice on a paved surface. Do you know how to avoid this invisible hazard? 

Black ice is one of the most common winter hazards, and, because it can appear without warning, one of the most dangerous. We all know to slow down in a snowstorm, but black ice is often encountered at normal driving speeds, leading to sudden loss of control. 

Black ice can form from rain, fog or condensation; if roads are wet and surface temperatures near or below freezing, be extra cautious. It frequently is caused by frozen snow or slush melt, which is why this winter hazard is often associated with nighttime or early morning driving. 

Sunlight on plowed roads and the heat generated by cars and trucks lessens the risk of encountering black ice, though it may persist in shady areas and less well-travelled streets. Black ice is also more common on bridges and overpasses because elevated roadways are surrounded by cold air. 

Safe Driving Tips for Black Ice

The best way to avoid black ice is to stay off the roads—listen to forecasts and heed warnings about icy conditions. If you must drive, go slow, use headlights at all times and increase your following distance, traveling 8 to 10 seconds behind the car in front of you.

If you find yourself on a patch of black ice, the best response is to do as little as possible until you leave the patch (most black ice patches are less than 20 feet long). Do not hit the brakes; allow yourself to slowly decelerate. Keep the wheel turned and eyes focused in the direction you want to go. If possible, head toward areas of visible traction, such as snow, textured ice, sand or gravel. 

Follow this rule of thumb if you start to skid: if the back end of the car is skidding, turn the wheel gently in the direction of the skid; if it is the front end, turn the wheel gently in the opposite direction. 

Safe Walking Tips For Black Ice

Black ice is a hazard for pedestrians, too. Wear boots or slip-resistant shoes if you expect to be walking in wintry conditions. To avoid slipping, walk like a penguin: take short steps, leaning forward slightly (this helps with stability by keeping the center of gravity over your feet). Keep your hands out of your pockets and extended outward. Always use handrails where available. 

Black Ice Parking Lot

Parking lots are a frequent site of black ice falls. Avoid parking in visibly wet or shady areas when possible, and take special care when getting in and out of your car, using the vehicle for support. (Photo: Jim Sturdivant)

Princeton University Facilities works hard to keep all walkways on campus free of snow and ice. If you notice a campus road, path or lot in need of clearing, contact the Facilities Service Center at 609-258-1000.

More Information

"How Black Ice Works" from How Stuff Works
AAA Winter Driving Tips
New Jersey Winter Driving Tips from NJ.Gov
"How to Drive on Black Ice" (PDF) from USDA.Gov. 
"How to Prevent Slipping on Ice This Winter" from Society blog's winter defense series.