Slippery conditions

Contents

Winter driving

The advantage of proper winter road conditions – that is, when it is really cold, snowing or when there is snow and ice on the road – is that you know that it is slippery and can adapt your driving accordingly. But even if you know it is slippery, driving in winter road conditions can still be risky and difficult.

When it is slippery it is of utmost importance to maintain a properly adapted speed at all times. If you drive too fast when it is slippery you will sooner or later end up in a situation where it is impossible to avoid an accident.


When it looks like this, you know it is slippery

Ice always makes the road slippery, making driving more risky and difficult. Snow can also make driving more difficult.

Polished snow

Slick polished snow can occur in all places where vehicles frequently stop and start. It is very common in busy junctions. Every time a vehicle stops in a snowy junction the snow melts, is polished and packed together and then freezes again when the vehicle drives on.


The snow becomes polished and slippery in places where vehicles frequently stop and start

Tracks of snow-free ground

When it has been snowing, tracks of snow-free ground on the road are often formed by traffic. Grip is normally better in these tracks than in the snow, but keep in mind that the road can still be slippery and if you accidentally drive outside of the tracks you may lose grip entirely.

Snow strings

Snow strings can occur on or beside the road long after it has stopped snowing. If possible, you should avoid driving on snow strings as the risk of skidding is very large on and around these. It is important to take snow strings into account if you are planning to overtake another vehicle.

Snow smoke

When it is very cold and snowing, or when it has snowed recently, vehicles disturb and raise fine particles of snow from the road, creating snow smoke which greatly reduces visibility. Snow smoke can occur anywhere but is more common in northern Sweden.

Drive carefully and maintain a safe distance to vehicles ahead when visibility is reduced due to snow smoke.


Snow smoke and drifting snow reduce visibility and can sometimes even make it difficult to see the road ahead of you

Drifting snow

Drifting snow is basically the same as snow smoke, but is caused by strong winds and is more common in southern Sweden.

Ploughed roads

When there is a lot of snow on the road, it can be very difficult to see road markings. When this is the case you have to rely on ploughing.

Once a road is ploughed, keep in mind that the plough truck may have cleared an area that is wider than the carriageway. To avoid driving outside of the carriageway and potentially skidding off the road, you must not drive too close to plough markers as they are located close to the edge of the ditch.


Plough markers show approximately where the ditch begins

Driving technique on slippery roads

When a road is slippery you must adapt your speed to account for both traffic and the road itself. If the road is winding you should reduce your speed well in advance of sharp bends. Further, if there are vehicles in front of you, you must maintain an appropriate following distance.

When you accelerate, do so gently, with a very light foot on the accelerator. If you accelerate too hard the car might start slipping, as the friction between the road surface and the tyres is low in slippery conditions.

You should normally drive in as high a gear as possible in slippery conditions. Doing so reduces the risk of the car losing traction, as the rate of acceleration decreases every time you change into a higher gear.


Drive in as high a gear as possible when the road is slippery

If your car loses traction in first gear when you are trying to start from a standstill, you can try to start in second gear instead. If this does not work you can try to reverse a little before attempting to move forward once again, as this often gives the tyres better grip.

However, if you need to reduce your speed when driving down steep inclines it is better to drive in a lower gear as this allows you to slow down using engine braking, which reduces the risk of wheel lock and lost traction.


Use engine braking when driving down steep inclines to reduce speed

To prevent skidding in very slippery conditions you should steer using small steering wheel movements.

Braking technique on slippery roads

When the road is slippery it is important to reduce your speed well in advance of sharp bends, exit slip roads, junctions and the like. If you start braking too late you risk driving off the road or causing an accident.

If your car is not equipped with ABS you can pump the brakes to help maintain control on slippery roads and to reduce the risk of wheel lock. When pumping the brakes you should gently apply and release brake pressure at a moderate rate.

If your car is equipped with ABS you should not pump the brakes. Instead, brake as hard as possible and let the ABS do all the work. With ABS, the wheels do not lock when braking, which means that you can continue to steer even when braking hard.

However, do not rely on technology too much – ABS can help you in some situations, but it won't make up for unsafe driving practices.

Braking distances on ice

Somewhat simplified, it can be said that braking distances on icy roads are usually 2-3 times longer with studded tyres and 3-4 times longer with non-studded winter tyres than they are on dry asphalt with summer tyres.

Note that these distances apply to vehicles with good tyres and brakes. On an icy road in a car with worn tyres and poor brakes, braking distances can be many, many times longer.

You do not need to be able to calculate braking distances on ice to pass the theory test. But you must know – for your own safety – that braking distances on icy roads are very long.


Braking distances on ice are many times longer than on dry asphalt

Black ice

Most people drive extra carefully when it is cold, snowing or when there is snow and ice on the road, because they immediately see and understand that the road is slippery.

The most treacherous road surface arises when the weather clears up after rain or fog and the temperature is around 0 °C. In these conditions so-called black ice may form. Black ice can occur very quickly when moisture on the road freezes to ice. Black ice is most common in winter but can also occur on cold days in spring and autumn as well.

The ice itself is not black, but visually transparent, allowing the often black road below to be seen through it. Black ice is thus very difficult to detect, especially in the dark.

Since road surface temperatures are usually much colder than the ambient temperature, you should expect roads to be slippery as soon as the thermometer shows +4 °C or colder. In some cars a dashboard warning light, usually resembling a snowflake, switches on when this is the case.


Frost warning

Places and conditions where the risk of black ice is increased:

Winter equipment

If you are surprised by a sudden snow storm, drive into the ditch or suffer engine failure and are stranded in the cold it is best to be prepared. You should always have the following equipment in your car when driving in winter conditions:


Always store proper winter equipment in your car during the cold months of the year

Winter tyres

Between December 1 and March 31 you are required to use winter tyres or equivalent equipment, if winter road conditions apply.

Winter road conditions apply when there is snow, ice, slush or frost on any part of the road. Keep in mind that the hard shoulder is also part of the road. In the event of a vehicle inspection, it is the police that determine whether winter conditions apply at a particular location.

Requirements regarding winter tyres

You are allowed to use non-studded winter tyres all year round (though this is not recommended). Studded tyres may also be used, regardless of the date, if winter road conditions apply or are expected. However, you are never allowed to use studded tyres on streets where studded tyres are prohibited.

Winter tyres used in winter road conditions must be marked with M+S (Mud and Snow) and have a tread depth of at least 3 millimetres. To get the best grip, you should replace winter tyres when the tread depth has been worn down to 4-5 millimetres.


Winter tyres used in winter road conditions must have a tread depth of at least 3 millimetres

You may use either studded or non-studded (so called friction tyres) winter tyres, but you must not mix – all tyres must be either studded or non-studded.

Studded tyres provide better grip and shorter braking distances on icy surfaces, but can result in longer braking distances on snow-free surfaces. If you are forced to brake hard on an icy road at 50 km/h, the braking distance will be approximately 40 metres with studded tyres and 50-60 metres with non-studded winter tyres. On snow, studded tyres and non-studded winter tyres are about equally effective.


The steel studs on studded tyres provide the best possible grip on icy surfaces, but can make the braking distance on snow-free ground longer than with non-studded winter tyres

On dry and warm asphalt, braking distances become much greater with both studded and non-studded winter tyres than with summer tyres. Accident statistics show that drivers who have used non-studded winter tyres are over-represented in fatal accidents when summer road conditions apply.

Read more about tyres

Slipperiness during spring, summer and autumn

The risk of slipperiness is obviously the greatest during winter, but roads can be slippery all year round.

Sudden temperature fluctuations, fog, wet leaves and pools of water are just a few examples of things that can lead to slipperiness, even though it is far from winter road conditions.

Spring

During spring it can sometimes be so cold that rain and melted snow freeze during the evening and night, resulting in so-called slippery spots. The risk of slippery spots forming is especially great in shady areas and on bridges and viaducts.


Bridges and viaducts can become very slippery as they are chilled from both below and above

Frost slipperiness can also be formed on snow-free roads during spring when the air's moisture freezes on the road surface. Frost slipperiness is most common at dawn and early in the morning after a cold and clear night. Fog can also cause frost slipperiness.

Drive carefully and be prepared for slippery roads after sudden temperature fluctuations and after cold evenings and nights.

Summer

Roads can be slippery in summer as well, both when the sun is shining and when it is raining.

When it is really warm and sunny, tar can penetrate out of the asphalt, making the road slippery.

When it rains after a heat wave, a slippery layer can be formed consisting of dust, exhaust emissions, oil residues and tyre deposits. Paving stones can become extremely slippery because of this. Grip is at its worst when it first begins to rain, as the slippery layer is eventually thinned out and rinsed off by continued rain.

Newly laid asphalt can also become very slippery when it is both rainy and sunny.

Autumn

In autumn, fallen leaves or soil and mud from agricultural machines can cause the road to be slippery, especially during and after rain. As in the spring, slippery spots and frost slipperiness can be caused by sudden temperature fluctuations and after cold evenings and nights.


Fallen wet leaves can make the road slippery

Aquaplaning

Aquaplaning can occur at any time of the year, if it is either raining or if there is water on the road for some other reason. Aquaplaning occurs when a vehicle's tyres are no longer able to divert surface water from their path. This leads to a layer of water building up in front of and under the tyres, effectively "lifting" them and removing their contact with the road.

Read more about aquaplaning

How to avoid skidding

When driving in slippery conditions you should drive in a manner that minimizes the risk of getting into dangerous situations. If you put too much faith in your car and your own driving skills you will sooner or later end up in a situation where it is impossible to avoid an accident.

This is of course the case when driving in normal conditions as well, but driving in slippery conditions is harder and requires more of the driver.


Losing control of your car during a skid can be a frightening and dangerous experience

Vehicle technology can help you in poor conditions to a certain degree. ABS reduces the risk of skidding and electronic stability control systems such as ESP detect and assist when the car is about to start skidding. However, never think that you can drive faster or with less safety margins just because your car is equipped with ABS and electronic stability control.

If the road is slippery, there is always a risk of skidding – especially if you drive too fast – regardless of how good you, your car and the car's tyres are. You must always adapt your speed, the distance ahead and your driving technique according to visibility, road surface conditions and prevailing traffic situations.


Driving too fast on a slippery road might cause you to lose control of your car

As part of your driver's licence training you will complete a compulsory risk course in two parts. The purpose of the second part is to teach you how to avoid getting into difficult and dangerous situations and to make you understand how, for example, speed affects your ability to cope with such situations.

Driving with a trailer in slippery conditions

When you drive with a trailer coupled to your car and apply the brakes there is a risk that the car will brake more effectively than the trailer. This risk increases if the road is slippery – especially on downhill slopes and in curves.

If this happens, the rear end of the trailer can, in a worst case scenario, slide to the right or the left – causing the car and trailer to fold up like a jackknife. This is called the jackknife effect and is a very dangerous situation as the vehicle combination becomes uncontrollable.


The risk of jackknifing when towing a trailer increases if the road is slippery

The best way to minimise the risk of jackknifing is to drive in a calm and careful manner that allows you to stop without having to brake hard.

Winter tyres on trailers

When you are required to use winter tyres and winter road conditions apply, the following rules apply:

You are allowed to:

You are not allowed to:

In other words, a trailer must have tyres that are as good or better than those on the car towing it.