Article

The perils of black ice

NZI Business Hub

Winter is a dangerous time for motorists with slippery roads, and for those travelling in the colder parts of NZ also having to contend with icy conditions. But in certain regions the more noticeable snow isn’t the only danger on the roads. The clear transparency of “black ice” means it often goes undetected until too late, posing a significant risk to motorists and contributing to a number of road accidents every year.

Black ice is a thin coating of clear ice on a road's surface. As the ice is transparent, the black of the road below is seen through (hence the name) and the ice is practically invisible to drivers. Like your standard ice, black ice is extremely slippery and offers vehicles very little traction which can lead to accidents for unfortunate and unwary drivers.

Black ice often forms after a light rain when the road surface is at zero degrees Celsius or lower. The water quickly freezes onto the road and as it usually doesn’t have any bubbles, the ice becomes practicably invisible. The occurrence is most common at night or early in the morning, however, the ice can last longer in cooler, shady areas where sunlight doesn’t reach. The phenomenon is also common on bridges with the cold air above and below the bridge working to keep the ground temperature low, maintaining the black ice longer. Likewise, on rural roads the ice can last longer as typically they have less traffic and the warmth and friction of traffic works to wear away the ice.

Drivers in these cooler areas need to maintain vigilance, particularly in May through August where temperatures are coolest. Before setting off in the early morning or evening inspect the road and footpaths, if it's dry but there are areas with darker, glossy patches that is likely to be black ice.

Black ice often forms after a light rain when the road surface is at zero degrees Celsius or lower. The water quickly freezes onto the road and as it usually doesn’t have any bubbles, the ice becomes practicably invisible.

If you suspect there may be black ice along your route, the safest prevention is to avoid driving until the temperature warms and the ice melts. However, if delaying the driving isn’t possible, drivers should slow down and increase the following distance between other vehicles. If you do hit a patch of black ice, remain calm and avoid any sudden braking or dramatic turning of the wheel. Instead, ease your foot off the accelerator and keep the steering wheel steady so when you regain traction the wheels are pointed the correct way.

Although running into black ice is often out of our control, awareness of the conditions that create the ice are vital to being prepared for it. If the conditions are suited for black ice, drivers need to be vigilant in looking for tell-tale signs before driving and subsequently driving to the conditions should it be a concern. These are key things we do have control over that can help keep us and other road users safer during the winter months.