Winter Driving: At What Temperature Are Icy Roads Most Slippery?

Winter Driving: At What Temperature Are Icy Roads Most Slippery?

January 29, 2020

Winter weather is perfect for cozying up inside, binging on Netflix, and nursing a cup of hot chocolate. Unfortunately, snow and ice have a habit of making an appearance during the workweek. Maybe you’re thinking of taking the day off, but you’re not sure if the roads are bad enough to warrant one.

This begs the question: At what temperature are icy roads most slippery? It turns out that icy roadways are especially dangerous in certain situations. And every driver should keep these conditions in mind the next time they’re on the road.

Protect yourself the next time ice makes an appearance. Here’s when icy roads are at their most dangerous, as well as some other winter driving tips.

At What Temperature Are Icy Roads Most Slippery?

It’s safe to say that icy roads are always dangerous. But some road conditions are worse than others. Over the years, plenty of researchers have sought to answer the question of when ice is at its most dangerous.

One of the most popular theories is that ice maintains a sleek liquid coating once frozen. It’s true that the surface of the ice is, of course, responsible for its slippery characteristics. However, this isn’t caused by the inexplicable presence of liquid water.

It comes down to the chemical structure of frozen water molecules. Weak connections in the crystalline water network are liable to come undone and roll like marbles across the surface. When your vehicle’s tires travel over the ice, it’s effectively sliding on microscopic ball bearings.

But let’s return to the topic at hand: When is this weak surface area most vulnerable to slipping? A collection of researchers discovered that the ideal slippage point occurs at a temperature of -7 degrees Celsius, or about 20 degrees Fahrenheit.

Temperatures colder than this point reduce the energy in the ice network and thus make it more difficult to break their weak bonds and roll across the surface.

Perhaps the most interesting aspect of this study revealed that we’ve already known the ideal slippage temperature. Without this research, skating and curling rinks have already been setting their ice in this temperature range.

When Do Roads Ice Over?

The freezing point of water is 32 degrees Fahrenheit. When you see a temperature posted online or on television, you should know that meteorologists are reporting the air temperature. Their measurement devices are located a few feet above the ground.

While the air temperature rests above 32 degrees Fahrenheit, the actual ground temperature could sit below this number. This is especially dangerous on clear nights when the surface temperatures lose heat quicker than the surrounding air.

For this reason, you should always be cautious of precipitation when the ambient air temperature sits at around 40 degrees Fahrenheit and below. Falling precipitation can hasten the speed at which the ground loses heat, contributing to sudden freezing.

Due to these different factors, there’s no clear indication when roads are icing over. You may even notice that meteorologists are not always sure when icing may occur.

Always practice your best judgment. If the air temperature is close to 32 degrees Fahrenheit, it’s best to avoid driving when precipitation occurs. It may be safe during a clear evening, but once the sun pulls away the lingering surface moisture can quickly turn to ice.

Common Types of Freezing Weather Conditions

You should familiarize yourself with inclement weather conditions that oftentimes result in icy roads. For example, do you know what freezing rain is? Or what about black ice?

Freezing rain guarantees you’ll encounter ice on the road. In the clouds, this rain hasn’t turned to snow because it’s above the freezing point. But as it plummets to the earth, it crosses over cold air that brings this liquid below freezing.

Once it hits the ground, it turns to ice. Freezing rain is especially dangerous as it tends to coat every surface of the roadway.

You may have also heard of black ice. This ice forms during a gentle rain shower or passing supercooled fog. When it freezes on a cold surface, it does so instantly, without the disturbance of wind.

The clear, undisturbed sheen of ice is known as black ice because it’s nearly transparent, so you only see the black asphalt underneath. It’s almost invisible to the naked eye, making it a worrisome road hazard.

How to Drive on Icy Roads

You should avoid icy roads whenever possible. But that isn’t always an option. For that reason, every car owner should know how to navigate treacherous frozen roadways.

The best tip is the easiest: Remember to slow down. Even at the posted speed limit, you’ll be likely to spin out if you come across an icy road.

Patches of ice can dramatically increase your stopping distance. Leave as much space as possible between you and the car ahead of you.

When you’re making a turn in icy conditions, never hit the gas in the middle of a turn. This could result in you spinning out. Instead, slow down in advance and then roll into the turn.

You can accelerate the vehicle once you’re on a straight roadway once again.

These are barely the basics of driving in winter weather. Refer to these tips for a detailed collection of winter driving strategies.

Stay Safe This Winter

You asked, “at what temperature are icy roads most slippery?” They’re worst at 20 degrees Fahrenheit. It’s best to avoid the drive altogether when the reported temperature is in that ballpark.

Unless you live on the equator, it’s a fact that you’ll be dealing with snow and icy roadways from time to time. Staying cognizant of different ice conditions can help keep you safe the next time you encounter these obstacles.