Winter Roads - Beware Black Ice

Navigating winter conditions on South Island roads requires awareness and caution, particularly regarding the notoriously dangerous phenomenon — black ice.

What is black ice in driving?

Black ice forms when moisture from fog, light rain or melted snow on the road drops to 0 degrees or lower.

When the air temperature drops below freezing, any moisture on the ground will freeze and form a thin, highly transparent, slippery and dangerous layer of ice. Any existing ice or snow on the ground will slowly melt when the temperature rises the following morning. The water can then re-freeze overnight, leading to hazardous driving conditions and an increased risk of car accidents.

This thin ice layer blends seamlessly with paved road surfaces — which is why it’s called ‘black ice’.  

Where is black ice likely to occur on the road in New Zealand?

You’ll find black ice in areas with sub-freezing temperatures. Common locations include the Southern Alps and frost-prone regions like Otago and Southland.

This thin, highly transparent ice layer is often found in corners shaded by trees or other objects since they receive less warmth from the sun during the day. Black ice is also common on bridges and overpasses – where the elevation allows cold air to flow under the surface of the road and lower its temperature. 

What does black ice look like?

How do you detect black ice? Look for:

• Dark, glossy patches on the footpath or road surface, especially in shady spots. 
• Other drivers braking or manoeuvring with extra care.

Image credit: Triplec85

If you’re planning on driving in icy conditions, clear any overnight condensation from your car windows. If black ice has formed on the road pavements, you’ll have optimal visibility to react promptly to any hazards. Wait for the sun to warm up the roadways and melt the ice whenever possible. 

While driving on snow allows some traction, black ice offers none. If you suspect black ice on your road surfaces, keep plenty of distance ⁠— more than you usually would in inclement weather. 

Avoiding black ice risks

Driving in New Zealand is relatively easy compared to many other countries, sometimes leading us to become complacent and overlook potential hazards. It's important, however, to remain aware of the risks of black ice on roads.

If your flight arrives late at night, consider delaying some or most of your driving journey until the next day. We understand the desire to maximise your time on the road or the slopes, but we've witnessed numerous instances where customers fly into Christchurch at midnight and proceed to drive straight through to Queenstown. Unfortunately, fatigue, black ice and unfamiliar roads can contribute to a higher risk of collisions. 

Should you drive on black ice? If you hit a patch of black ice, try not to panic. If you brake too hard on black ice, this can cause the car to slide. Instead, ease your foot off the accelerator and keep your steering wheel straight to avoid sliding and losing control. Gradually reduce speed and let the vehicle stop on its own if you have enough room ahead. 

Responding to black ice incidents

If you encounter a black ice-related accident, here are a few tips:

• Slow down and approach the area with caution, keeping a safe distance. Turn on your hazard lights to alert other drivers.
• If the accident involves injuries or significant damage, dial 111. Follow instructions and provide any assistance you can.
• If you have first aid training and it's safe to approach the scene, check if anyone requires immediate medical attention. Offer assistance within your capabilities. 
• Remain calm, patient and respectful towards others. Support and reassure those affected by the accident while waiting for help.

Remember, your safety should always come first. If you feel uncomfortable assisting, wait for emergency services. 

More about black ice

How long does black ice last?

Black ice can linger for hours, especially in shady spots where the sun doesn't reach. It tends to form overnight and stick around until the morning sun warms the road enough to melt it.

Where does black ice form?

Black ice forms in corners shaded by trees, on bridges, and on quiet rural roads with little traffic to wear it away, and it can hang around well into the day. Keep in mind that even after a thaw, lingering patches can remain. 

When is black ice likely to occur on the road?

Black ice is most common at night and in the early morning, particularly during the colder months, especially on frosty nights and early mornings. You're most likely to come across it in certain regions like Otago and Southland, along with the Southern Alps and other frost-prone parts of the South Island. Bridges, overpasses and shaded corners are the usual trouble spots. 

How dangerous is black ice?

Black ice offers very little traction, and because it's transparent against the black asphalt road beneath, you often won't spot it until you're on it. Add in icy conditions, fatigue or unfamiliar roads and the risk of a collision climbs quickly. The good news is that with a bit of awareness and caution, it's a hazard you can manage.

How fast should you drive on black ice?

As slowly and gently as possible. Black ice offers very little traction, so drop your speed well below what you'd normally do in wet weather and leave plenty of distance between you and the car ahead. Keep an eye out for other drivers braking or manoeuvring with extra care — that’s a warning sign that black ice is about.

Help keep New Zealand roads safe!

Understanding the risks of black ice on the road and how to respond can make a significant difference in navigating challenging conditions on wet roadways in New Zealand. 

Share these tips with friends and family to promote safer journeys!

Book great rental vehicle deals with Omega today – and find even more valuable advice and road trip ideas on our blog.

Have a safe and happy journey this winter and let the only bruises be incurred on the slopes!