The Basics of Black Ice

With more than 70% of U.S. roads located in regions receiving an average of five inches of snow or more annually — and nearly 70% of the nation’s population also living in those areas — safe winter driving is a necessity. However, as climate patterns shift, bringing more extreme weather and extending it into new areas, drivers — and departments of transportation — unaccustomed to such conditions are facing new seasonal challenges. Perhaps one of the most dangerous is black ice.


What is black ice?

This thin coat of ice can form on roadways and bridges in multiple scenarios, and because it is transparent, it visually blends into the pavement, taking drivers by surprise. Sometimes, the only clue to its presence is at night when its shiny surface may reflect in the headlights. It’s important to note that snow does not need to be present for it to form, making it a problem not only in winter but also in late fall and early spring.


What causes black ice?

Black ice occurs when there is moisture on the road, usually from snow and ice melting on or near the roadway. It can also happen when precipitation in the form of drizzle, rain, or fog lands on the road. As road surface temperatures drop below freezing, the thin sheet of water freezes, forming nearly-bubbleless ice. It can be prevalent during freeze-thaw cycles and is most common in the early morning or at night when temperatures are at their lowest and before the sun rises, warming road surface temperatures. Likewise, as the sun goes down, the road surface can cool quickly, supporting the formation of new ice.

Black ice can also occur during rush hour in sub-zero temperatures or near traffic lights and on-ramps, where exhaust from stopped or slow-moving traffic freezes upon contact with the pavement and is a frequent cause of large numbers of accidents and major delays.

Bridges and overpasses are other common locations for black ice formation, as cold air can flow beneath the elevated surface, lowering pavement temperatures. Shaded areas are another potential problem area, as it can be difficult for the sun to warm the pavement during the day.

Common areas for Black Ice

How can drivers better handle black ice?

Be alert — especially when driving late at night or in the early morning hours, particularly in heavy, slow traffic. Look for glossy patches of road and be sure to adapt how you drive to the conditions at hand. Maintain more distance between you and the vehicle in front of you to give you more time to react.

If you hit black ice, do not try to overcorrect.

  1. Don’t slam your brakes, which can cause you to skid and lose control. If you must brake and your vehicle has an antilock braking system (ABS), put firm pressure on your brakes. If you don’t have an ABS, gently pump your brakes.
  2. To avoid swerving into traffic, firmly hold your steering wheel straight to keep your vehicle’s wheels straight. If you start to drift, make only small corrections to keep your vehicle in control. Steer in the direction you want to go.
  3. Take your foot off the gas to decelerate or downshift to gain more control over your vehicle.
  4. Look for areas with traction, such as gravel or snowpack, where you can regain additional control.
  5. Stay calm — black ice typically forms in patches, and you’ll come out on the other side, but you may experience a small jolt as your tires find purchase. If you can’t avoid going off the road, look for an empty spot or a snowbank.
  6. If you need to pull over, only do so when it’s possible to do it safely. Look for areas where you’re less likely to be hit by another vehicle, such as a parking lot. In areas with black ice, the shoulder of the road can often be a dangerous place.

Preparedness is key. Before you hit the road, be sure to check your local weather and road reports. Many departments of transportation offer online updates, notifications, or apps. When possible, avoid driving in adverse conditions or heavy traffic. If you see ice developing on your car windows or mirrors, it’s a clear sign the temperatures are changing, warranting added caution. Note that black ice can also form on driveways and sidewalks, so always be aware of your surroundings whether in your car or on foot.


How can road maintenance professionals manage black ice?

While it’s impossible to avoid black ice entirely, there are resources to help you accurately anticipate potential risks and take proactive measures to keep drivers safer and traffic flowing.

With powerful weather and pavement insights, risk management tools, and route-specific treatment recommendations, you can get ahead of conditions and make the best use of your people, treatments, and fuel. One leading option is ClearPath Weather® from DTN, which supports data-driven decisions that help you effectively manage winter road weather issues before, during, and after an event.


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