Black ice explained
By Allstate
Last updated: January 0001
Black ice is a nearly invisible layer of ice that sometimes forms on roads and sidewalks under specific conditions. It blends in with the pavement or road creating a serious safety risk for pedestrians and drivers alike. In this article, we’ll cover what black ice is, how and where it forms, why it’s dangerous, how to spot it, and how to navigate it safely.
What is black ice?
Black ice, also known as glaze, is a coating of ice that is generally clear and smooth, according to the American Meteorological Society (AMS). Black ice is typically characterized by its transparency, making it nearly impossible to spot.
How does black ice form?
Black ice forms when a film of supercooled water freezes on an exposed object or surface, such as a road, according to the AMS. The water can come from any source, such as melting snow, rain, fog, or even a drizzle.
Where is it most common?
All that’s required for black ice to form is a small amount of water and a surface to freeze on, meaning it can happen anywhere. It’s most common in places where there’s less warmth from the sun, including heavily shaded roads, underpasses, tunnels, and the bottom of hills. Bridges and overpasses are also prone to black ice formation due to the circulation of cold air beneath them, cooling the pavement above them, according to Washington State University (WSU).
What makes black ice so dangerous?
Black ice is dangerous because it is extremely slippery and difficult to spot. Even experienced drivers can be caught off guard, leading to an increased risk of accidents. The U.S. Department of Transportation (DOT) reports that 24% of weather-related vehicle crashes occur in snowy, slushy, or icy conditions.
How to spot black ice
Steps to take at home
It is important to take measures to reduce ice formation at your home. This is to reduce the chances of accidents happening when walking around your property or driving in and out of your driveway.
To accomplish this, you can consider pretreating your driveway with anti-icers or you can use non-chemical options such as cat litter, sand, gravel, or other options to help increase grip for pedestrians or vehicles, according to This Old House.
Steps to take when driving on the road
One of the most important things to remember to do when driving in inclement weather conditions is to slow down. Slower speed, slower acceleration, and slower braking increase your overall control of your vehicle, according to the Illinois Department of Transportation. Keep an eye out for black ice in areas where it commonly occurs.
What to do if you drive over black ice
If you encounter black ice, stay calm. If you lose control of your vehicle, don’t do anything immediately. Keep the steering wheel as straight as possible and lift your foot off the accelerator. Do not hit the brakes. That can make it worse, according to Gallagher Bassett.
Black ice is typically found in patches and rarely exceeds a 20-foot stretch. Riding out the ice and then regaining traction is typically the best approach to navigating these situations.
Black ice FAQs
Yes. Pavement cools more slowly than the air. Moisture can refreeze on the pavement even if the air temperature is above freezing.
Despite its common name, black ice is actually typically transparent, which allows the dark pavement to show through. Its more official name is glaze, according to the American Meteorological Society.
Tire chains can make your vehicle slow down a bit faster on black ice, according to Highland Tire but generally these are meant for traction in snow. They do not necessarily make a big difference when driving over black ice.
In ideal circumstances, your tires would be as close to new as possible for driving in snow and ice. That gives you the best grip possible in slippery conditions. That said, if you’re driving in winter conditions, you should have at least 5/32” of tire tread left, according to Tire Rack.