Winter driving tips - snow & ice
Winter conditions can be unpredictable, however most of the techniques which are required in cold environments are common sense:
- Keep speed as low as practically possible
- Increase the distance between cars, corners, junctions and any other hazards
- Get all of your braking done on the straights, never brake during a corner
- Be prepared for understeer and oversteer, and know how to correct
- Be prepared to use ABS or avoidance braking techniques
- Top up washer fluids and antifreeze
Many websites have published information which deal with the above issues well, so if you need more of the basics, try a Google search. This article discusses some of the more advanced safety based driving techniques for making progress in winter driving conditions.
Introduction to winter driving techniques
Making the most of the available traction is key to winter driving. Loss of traction can lead to wheelspin under acceleration, wheel lock under braking and sideways sliding while cornering. There are now many computer controlled systems which can control these actions to a limited extent, however there is no substitute for driver skill.
Investing in a vehicle with ABS is the single most effective method of increasing your safety in slippery conditions. Traction control systems can control wheelspin, but bear in mind that these systems are reactive, which means you'll have to be in a certain amount of trouble before they will start to operate. Much better to avoid the problems to start with.
Tips for driving on snow and ice
- Pull away and accelerate gently and progressively. In slippery conditions such as snow and ice, aggressive acceleration will almost certainly break traction at the driven wheels. The resulting wheelspin can lead to loss of steering control in a front wheel drive (FWD) car, or an oversteer slide in a rear wheel drive (RWD). Both of these situations will prevent you from going in the direction you want and can be difficult to recover from.
- If you do notice wheelspin (or the traction control systems fighting for grip), don't floor the throttle, instead back off the gas and then reapply smoothly.
- Best practice is to keep engine revs low in order to maximize your grip in winter conditions. Keep a constant gentle throttle for best results.
- Change up sooner rather than later, pull away in second gear if possible, and use the highest practical gear at all times. This reduces the torque at the driven wheels and will therefore reduce the chances of wheelspin – also a useful trick when trying to climb a slippery muddy hill.
- Avoid any sudden driver inputs (such as steering, braking, acceleration or gear changes). You only have a finite level of grip available and you don't want to overload your tyres unnecessarily. Driving smoothly will conserve grip, and make you a safer driver.
- Brake soon, and gently. Be prepared to ease off the brakes (if you do not have ABS fitted) in order to steer. Locked wheels cannot steer!
- If you do have ABS, you'll be able to tell it has triggered by feeling a pulsing sensation through the brake pedal. If this has occurred do not 'pump' the brakes – rather keep a firm pressure on the pedal for maximum effectiveness. ABS is designed to help you steer as you're slowing down so use this to your advantage and avoid obstacles.
- Even if you do have ABS fitted, don't get into the habit of using the system routinely - you'll be able to slow down in a shorter distance if you use threshold braking techniques.
recovering from slides in very slippery conditions
Note: If you're an experienced driver you may be able to use other techniques to help recover from these situations, and these are covered in the dedicated oversteer and understeer articles.
Understeer is when you turn the steering wheel but find that the car has a tendency to continue straight ahead (Figure 1). Oversteer is when the car tries to spin round due to a lack of traction at the rear (Figure 2). Both situations are more likely on winter roads but can be helped using the same techniques (which should make things easier to remember).
Figure 1: Understeer - the car continues straight on despite applying steering lock
Figure 2: Oversteer - the rear of the car breaks loose and a spin is likely if not corrected
If you do find yourself in an understeer or oversteer situation on a very slippery road do not stamp on the brakes in panic as this will make things much worse. Point the steering in the direction of intended travel, but don't use excessive steering lock, if a car starts to understeer many people will panic and apply as much steering lock as they can, but this can make the car even less likely to make the turn. When traction is regained, be prepared to take off the steering lock quickly in order to prevent another slide in the opposite direction.
You also need to try and get the driven wheels turning at road speed and regain some traction. Pressing the clutch or flicking an automatic into neutral will remove the influence of the engine and help get the wheels rotating at a more natural rate. With luck, this will create vital grip for avoiding obstacles and allow you to progressively apply the brakes.
Cars with electronic stability controls fitted
An example stability control indicator light
If your car is fitted with electronic stability control systems such as DSC or ESP (or other related acronyms) the car can automatically reduce throttle and brake individual wheels when necessary to maintain control. If this is the case, ensure the system is turned on (usually on by default) and make sure your steering is pointing in the intended direction - the car will do the rest. Modern traction and stability control systems will automatically make the best possible use of available grip and help you avoid an accident. If in doubt, gently use the brakes to slow to a halt.
Winter tyres
Depending on the severity of the conditions, it may be worth considering specialist winter tyres. These vary from a Mud and Snow (M&S) rating through to studded tyres for icy roads. Surprisingly, with the correct tyres fitted, driving in quite severe conditions can become remarkably easy – you just have to pay a visit to Finland or other northern countries in the Winter for a demonstration.
Manufacturers of winter tyres use several methods to increase friction and help maximize control. Firstly, the rubber compounds are usually softer which allows optimum friction to be reached at lower temperatures (this however does make them wear faster when used in warmer conditions on dry tarmac). The diagram below shows the effect of different rubber compounds on the stopping distances in different temperatures.
Source: http://conti-central.co.uk/winter-tyres/
Secondly, winter tyres can have small 'sipes' which are formed into the rubber within a tread block - these provide grippy edges which are especially useful when driving in snow. Thirdly, the tread tends to be wider and deeper which provides more bite when driving in the snow or on ice.
Sipes: the horizontal lines shown in the image below.
Deeper tread provides more 'bite'
Winter tyres usually also have an aggressive block-like tread pattern which can help to dig into the snow and provide traction (also useful in muddy conditions). Finally, small studs can be fitted to the tyre and these provide a great deal of benefit when driving in icy conditions, although in some countries these are only permitted in the coldest months as they damage road surfaces. Studded tyres can also increase your braking distance when on a clear dry road.
Snow chains
If you're driving in deeper snow, it might be worth considering using snow chains, or at least having some in stored in your car. These are fitted to the driven wheels and can provide dramatic increases in traction. If you do choose to fit snow chains, ensure the manufacturer's instructions are followed carefully or damage to your car could result.
Stopping distances in varying winter conditions
Finally, we'll take a look at stopping distances to emphasise how important it is to slow down and brake early. Graph 1 shows the dramatic difference in braking distance when on black ice compared to normal tarmac conditions, it's well worth bearing this in mind in the winter an adjust your driving style accordingly.
Graph 1: Stopping distance vs speed for dry asphalt and black ice
Source: http://www.csgnetwork.com/stopdistcalc.html
Friction levels in different winter conditions
Graph 2 below summarises the levels of friction available in different winter conditions - the worst conditions observed provided only approximately a quarter of the grip of dry asphalt.
Graph 2: Grip levels in different conditions (calculated as the coefficient of friction)
Please take care on the roads this winter, and feel free to read our other winter driving tips below.
